Information

What are the effects of muscle and fat mass on survivability?


If we have humans A, B and C who are different:

  • A is thin (skinny) without significant muscle or fat mass.
  • B is muscular
  • C is fat

Which one of them has the best body for survival in accidents like car crash, aircraft crash, fall from the ladder, fall down the stairs, being hit by a car, slip in the bathroom, etc?

What are the effects of muscle and fat mass on survivability?


For car crashes, it's a mixed bag:

Basically, it looks like, if wearing a seat belt, slightly overweight is more likely to survive a car crash, but if no seat belts are worn they are at a disadvantage; the very obese are always more likely to die, however. Also, some of this was found only for males, not females.


Muscle Atrophy

The word muscle atrophy comes from the Greek a (without) and trophe (nourishment). It refers to the breaking down of muscle fibers and is usually described as occurring in skeletal muscle however, cardiac and smooth muscle also atrophy. Muscle atrophy mechanisms are divided into three groups – physiologic, pathologic, and neurogenic. While some forms can be reversed, others cannot.


To Gain Muscle And Lose Fat, Drink Milk, Study Suggests

Part of an ongoing study into the impact of drinking milk after heavy weightlifting has found that milk helps exercisers burn more fat.

The study by researchers at McMaster University and just published in the American Journal of Clinical Nutrition, was conducted by the Department of Kinesiology's Exercise Metabolism Research Group, lead by Stuart Phillips.

The researchers took three groups of young men 18 to 30 years of age -- 56 in total -- and put them through a rigorous, five-day-per-week weightlifting program over a 12-week period. Following their workouts, study participants drank either two cups of skim milk, a soy beverage with equivalent amounts of protein and energy, or a carbohydrate beverage with an equivalent amount of energy, which was roughly the same as drinking 600 to 700 milliliters of a typical sports drink.

Upon the study's conclusion, researchers found that the milk drinking group had lost nearly twice as much fat - two pounds - while the carbohydrate beverage group lost one pound of fat. Those drinking soy lost no fat. At the same time, the gain in muscle was much greater among the milk drinkers than either the soy or carbohydrate beverage study participants.

"The loss of fat mass, while expected, was much larger than we thought it would be," says Phillips, associate professor of kinesiology at McMaster. "I think the practical implications of these results are obvious: if you want to gain muscle and lose fat as a result of working out, drink milk."

As reported in the first phase of the study, the milk drinking group came out on top in terms of muscle gain with an estimated 40 per cent or 2.5 pounds more muscle mass than the soy beverage drinkers. In addition, this group gained 63 per cent or 3.3 pounds, more muscle mass than the carbohydrate beverage drinkers.

"I think the evidence is beginning to mount," says Phillips. "Milk may be best known for its calcium content in supporting bone health, but our research, and that of others, continually supports milk's ability to aid in muscle growth and also promote body fat loss. To my mind -- with milk being a source of nine essential nutrients -- it's a no brainer: milk is the ideal post-workout drink for recreational exercisers and athletes alike."

Ongoing work with this project will focus on the components of milk that might be responsible for the effects observed by the McMaster-based researchers. The work was supported by grants from the Canadian Institutes for Health Research and a grant from the US National Dairy Council.

Story Source:

Materials provided by McMaster University. Note: Content may be edited for style and length.


How diabetes causes muscle loss

Diabetes mellitus is associated with various health problems including decline in skeletal muscle mass. A research group led by Professor Wataru Ogawa at the Kobe University Graduate School of Medicine revealed that elevation of blood sugar levels leads to muscle atrophy and that two proteins, WWP1 and KLF15, play key roles in this phenomenon. These findings were published on February 21 in the online edition of JCI Insight.

Muscle mass decline associated with ageing impairs our physical activity, making us susceptible to a variety of health problems and thus leading to shortened lifespans. Age-dependent muscle mass decline and the consequent impairment of physical activity is known as "sarcopenia," a serious health burden in aging societies.

We already knew that patients with diabetes mellitus are prone to muscle loss as they age, but an underlining mechanism for this phenomenon remains unclear. Diabetes mellitus is a disease caused by insufficient action of the hormone insulin. Insulin not only lowers blood sugar levels, but promotes the growth and proliferation of cells insufficient action of insulin has been thought to result in the suppression of growth and proliferation of muscle cells, which in turn contribute to the decline in skeletal muscle mass.

Professor Ogawa's research team made the surprising discovery that a rise in blood sugar levels triggers the decline in muscle mass, and uncovered the important roles of two proteins in this phenomenon. They found that the abundance of transcription factor KLF15 increased in skeletal muscle of diabetic mice, and mice that lack KLF15 specifically in muscle were resistant to diabetes-induced skeletal muscle mass decline. These results indicate that diabetes-induced muscle loss is attributable to increased amounts of KLF15.

The team investigated the mechanism for how the abundance of KLF15 is increased in skeletal muscle of diabetic mice. They found that elevation of blood sugar levels slows down the degradation of KLF15 protein, which leads to an increased amount of this protein. Professor Ogawa's team also discovered that a protein called WWP1 plays a key role in regulating the degradation of KLF15 protein.

WWP1 is a member of proteins called ubiquitin ligase. When a small protein called "ubiquitin" binds to other proteins, the degradation of the ubiquitin-bound proteins is accelerated. Under normal conditions, WWP1 promotes the degradation of KLF15 protein by binding ubiquitins to KLF15, keeping cellular KLF15 abundance low. When blood sugar levels rise, the amount of WWP1 decreases, which in turn decelerates the degradation of KLF15 and thus the increase in the cellular abundance of KLF15.

This study uncovered for the first time that elevation of blood sugar levels triggers muscle mass decline, and that the two proteins WWP1 and KLF15 contribute to diabetes-induced muscle mass decline.

As well as diabetes mellitus, other conditions such as physical inactivity or ageing result in muscle mass loss. The proteins KLF15 and WWP, which have been shown to contribute to diabetes-induced muscle mass loss, may also be related to other causes of muscle loss. Currently, no drug is available for the treatment of muscle loss. Professor Ogawa comments: "If we develop a drug that strengthens the function of WWP1 or weakens the function of KLF15, it would lead to a groundbreaking new treatment."


Bone Mass Loss

Bone mass loss is a condition known as osteopenia. Osteopenia often progresses to osteoporosis, a condition characterized by the reduced bone mineral density and increased rate of bone loss [10]. Bone mineral density decreases with age. Therefore, the probability of a person suffering from osteopenia or osteoporosis, and related skeletal fragility increases with age [10].

The causes leading to bone mass loss are multifactorial and similar to the causes of muscle mass loss. The most common cause of osteopenia is aging. Skeletal aging is known to progress faster in women than in men due to hormonal changes after menopause [10]. However, genetics, nutritional factors, lifestyle factors, and comorbidities have been shown to be associated with bone mass loss [10, 31]. During the later years of an individual’s lifespan, there is an accelerated loss of bone tissue, which is probably related to genetic factors [32, 33]. There are multiple genes involved in the control of musculoskeletal interactions [34, 35, 36, 37], such as the alpha actinin-3 (ACTN3) and the myocyte enhancer factor 2C (MEF2C) gene. Alpha Actinin-3 regulates the muscular power performance and it is associated to decreased bone mass, whereas Myocyte Enhancer Factor 2C is responsible for controlling bone development by means of activating chondrocyte hypertrophy [37]. With “normal” aging, there is a marked increase in the formation of advanced glycation end-products (AGEs) [37]. In bones, AGEs enhance osteoclast-induced bone resorption, modify bone proteins and disturb bone remodeling [37, 38]. In addition to genetics, the whole process of maturation, development, and decline of the musculoskeletal system is significantly affected by environmental influences [39]. An example of an environmental factor would be a fall, which can increase the possibility of developing osteopenia and osteoporosis [39]. In females, at the beginning of menopause, the acute loss of the restraining effect of estrogen on osteoblasts and osteoclasts membrane receptors leads to accelerated bone turnover and the uncoupling bone formation from resorption [40]. The imbalance between calcium secretion and absorption following the estrogen depletion has been suggested to influence the accelerated bone loss rate in women [10]. Calcium and vitamin D deficiency may increase the possibility of suffering from accelerated bone mass loss. High alcohol intake and smoking can also contribute to bone loss [41]. In addition, high alcohol intake is associated with increased bone loss, falling, and fractures in older men [42]. Smoking increases the risk of a fracture and osteoporosis [41].


Materials and methods

Considerable effort was made to use valuable research animals in the most efficient and responsible manner possible. Eighteen adult cats Felis silvestris catus were donated to the study by the UW-Madison Psychology Department. These cats were otherwise scheduled for euthanasia. The skeletons and their respective morphological measurement records were donated to the UW Zoological Museum, where they are documented as voucher specimens and are available for examination by museum guests.

Five (two males and three females) of the 18 cats donated by the Psychology Department were part of a study in which lesions of the visual cortex were made to one side of the brain (a unilateral lesion). The purpose of that research was to study the method of physiological compensation by remaining brain areas after early visual cortex damage. Four of these cats received this lesion when they were eight weeks old, and the remaining cat received the lesion when she was only one day old. Because the jump performance of these lesioned cats was not significantly different from non-lesioned animals, and because there was no difference in the amount or intensity of training required to induce maximal jumps between the two groups, no distinction was made between them in the analyses presented here.

Test subjects

A total of 18 domestic cats (13 intact females and five neutered males),ranging in body mass from 2.66 kg to 7.93 kg, was used in this study. All cats were at least two years old and not more than 10 years old, were in excellent physical health and were accustomed to frequent human contact. Cats were housed in metal wire mesh kennels (1.9 m high×1.6 m long×1.1 m wide) with concrete flooring and had access to resting boxes and wooden shelves within these cages. They were provided with Science Diet cat food(Hill's company, Topeka, KS, USA) and water ad libitum until 18-24 h before a jump training or video-taping session (see below).

Jump training

Between three and six sessions were devoted to acclimating each cat to lab surroundings before jump training was initiated. During these 20-45 min acclimation sessions, cats were allowed to roam freely in the lab and had access to canned, moist cat food. Cats were not allowed inside the jump enclosure during these sessions.

Each cat was subjected to a schedule of jump training sessions before maximum jumps were recorded on video tape. Between two and seven jump training sessions, each 20-60 min long, were required to train each cat to jump maximally. Cats participated in one jump training session per day. Food was withheld from the cats 18-24 h before each of these sessions. After each jump training session, animals were allowed access to their food for at least 60 min before it was again removed in anticipation of the following day's lab session, if one was scheduled.

Cats were trained to jump inside a rectangular enclosure (2.4 m high×0.9 m long×0.4 m wide see Fig. 2) made of Plexiglas and masonite. This enclosure limited the direction and height of each jump. Cats were introduced to the enclosure through a trap door and were then placed on an adjustable takeoff platform inside the enclosure. Cats jumped from this takeoff platform to a stationary landing box (0.30 m × 0.45 m ×0.40 m) mounted on the upper left edge of the enclosure. The position of this platform, and thus the jump height, was adjustable.

Diagram of jump enclosure. Cats took off from an adjustable platform and jumped upwards to the stationary landing box.

Diagram of jump enclosure. Cats took off from an adjustable platform and jumped upwards to the stationary landing box.

A training protocol was designed such that placement inside the jump enclosure stimulated jump behavior. In an effort to obtain maximal jumping performances, rewards were offered as soon as each cat successfully jumped to the landing box. Rewards were canned cat food accompanied by affection(petting) from an observer and, ultimately, removal from the enclosure. If jumps were not spontaneous, the takeoff platform was shaken and/or the cat was squirted with water until it jumped to the landing box. In this way, the takeoff platform was presented as an unpredictable, unstable environment,while the landing box represented a safe haven for each cat where rewards were available. Perhaps most importantly, each cat learned that jumping to the landing box was the only means of exit from the enclosure.

After each jump, cats were allowed to eat food and/or receive affection for approximately one minute before being removed from the landing box. Cats that ignored the food and affection attempts, and instead tried to jump out of the landing box, were removed immediately. The takeoff platform was then lowered by 5-10 cm, and the cat was returned to the takeoff platform through the trap door. This procedure continued until the cat had made between five and 10 total jumps or until the cat struggled in an obvious way to reach the landing box. No more than 10 jumps per session were allowed in order to minimize fatigue effects. Cats made approximately 10 jumps before becoming visibly fatigued. During subsequent sessions, the takeoff platform was lowered to within 5 cm of each cat's previous maximum jump, and the process continued until an approximate maximum height was achieved (i.e. the last height at which the cat successfully made it to the landing box, but only after an obvious struggle).

Measurement of takeoff velocity

At least 24 h after an approximate maximal height was determined for each individual during training, each cat was video-taped jumping to this height. Approximate maximal heights were either matched or exceeded on video-taping days. Maximum vertical jump height for each cat was defined as the last successful jump to the landing platform before consistent misses at the next greater height (i.e. just 5 cm higher). TOV was measured from high-speed videos of the takeoff portion of each cat's maximum jump. The maximum TOV for each cat was measured on two different days in order to determine the repeatability of each individual's performance. The highest TOV of these two days was considered to be the maximum performance. Cats performed no more than 10 jumps on video-taping days and were weighed within 24 h of their maximal jumps.

The movement of reflective markers placed on the cat's body was used to measure the maximum velocity of overall body center of mass (CM) position during the takeoff period. These movements were recorded by a high-speed (200 frames s -1 ) video camera. Each cat was labeled with reflective dots to indicate the location of the following anatomical landmarks: mid zygomatic arch (head), spinous process of scapula at anterior border, humerus greater tuberosity (shoulder), lateral epicondyle (elbow), styloid process of ulna(wrist), thoracic—lumbar vertebral junction (T13), iliac crest, greater trochanter (hip), lateral epicondyle of the femur (knee), lateral malleolus(ankle) and metatarso—phalangeal joint (5th MT) (see Fig. 3).

Digital video frames showing typical stages of the takeoff period preceding cat jumps: (A) deep crouch, (B) mid-takeoff and (C) full extension of torso and hind limb at takeoff. Note the three calibration lines (joined, forming two right angles) in the background and the reflective dots designating the 11 anatomical landmarks whose movement was used to calculate maximum takeoff velocity (TOV).

Digital video frames showing typical stages of the takeoff period preceding cat jumps: (A) deep crouch, (B) mid-takeoff and (C) full extension of torso and hind limb at takeoff. Note the three calibration lines (joined, forming two right angles) in the background and the reflective dots designating the 11 anatomical landmarks whose movement was used to calculate maximum takeoff velocity (TOV).

At least one day prior to video-taping, the 11 anatomical landmarks were shaved, external measurements of body segments between anatomical landmarks were made, and the left side of the cat's body was dyed black. Body segment measurements were used to calculate the CM for each segment (see below). Cats were anesthetized with halothane gas during this process. The reflective dots were attached to the marked anatomical points using rubber cement paste on the day of video-taping. A black `calibration' backdrop inside the jump enclosure was used to convert video digitization units into real distance measures. The takeoff platform was narrowed so that cats jumped perpendicular to the camera.

Spotlights illuminated the reflective dots on the cat's body as it jumped. Videos were taken using a Nac MOS-TV 200/60 high-speed video camera. The x—y coordinates of each dot were manually digitized by projecting the video image onto a piece of graph paper using a stop-action VCR and liquid-crystal display (LCD) projector. Videos were digitized at a rate of 100 frames s -1 . A customized computer software program was written to compute the overall body CM position from the mass of individual body segments, the CM location for each of these segments, and the position of segment CMs over time. Regression equations reported by Hoy and Zernicke(1985) to predict segment masses from body mass and segment length in domestic cats were used in this algorithm. The location of this overall CM was located at three key positions during the jump: the last frame showing hind paw contact with the ground(`takeoff'), and one frame before and one frame after takeoff. TOV was defined as the change in CM position over the three frames surrounding and including takeoff (a 0.02 s time span).

Hind limb dissections and body fat measurement

A standard euthanasia procedure was used in which each cat was first anesthetized with halothane gas. An injection of sodium pentobarbital was then administered intravenously in the femoral vein until all respiratory and cardiac activity had ceased. Hind limb muscles were dissected and measured within 2 h of euthanasia.

The three hind limb muscles analyzed in this study were the semimembranosus(hip extensor), the vastus lateralis (knee extensor) and the lateral gastrocnemius (ankle extensor) (Fig. 4). All of these muscles have been shown to be electrically active during cat jumps (Zomlefer,1976 Smith et al.,1977 Zomlefer et al.,1977 Walmsley et al.,1978 Zajac et al., 1981, 1983 Zajac, 1985 Abraham and Loeb, 1985). These muscles were removed from the right leg. They were separated and cut at the termination of muscle fibers at the origin and insertion, and the mass of each muscle was recorded. Dissected muscles were placed on ice in a standard freezer until all dissections were completed and were then transferred to a-80°C freezer and stored until fiber type analysis. The individual masses of these three muscles were summed to give total muscle mass. We chose to use these three muscles rather than all of the extensor muscles because each of the three chosen muscles is a major extender of its respective joint and each is easily dissected.

Diagram of the left hind limb bones of a cat showing the three extensor muscles measured in this study: semimembranosus (hip extensor), vastus lateralis (knee extensor) and lateral gastrocnemius (ankle extensor).

Diagram of the left hind limb bones of a cat showing the three extensor muscles measured in this study: semimembranosus (hip extensor), vastus lateralis (knee extensor) and lateral gastrocnemius (ankle extensor).

The entire left limb was removed by cutting through the ilio-sacral and pubic articulations. After removal of all muscles and tissues from the leg,the lengths of the femur, tibia, tarsals and third metatarsal were recorded and summed to give a total hind limb length value. After removal of the left leg and the three extensor muscles from the right leg, the percent fat content of the carcasses was measured using a DPX-L X-ray bone densitometer (version 1.5g, copyright 1988-95, Lunar Corp., Madison, USA). Fat mass was calculated for each cat as the product of % body fat and whole body mass. Lean body mass was computed by subtracting fat mass from whole body mass.

Myosin heavy chain analysis

The MHC Type IIb isoform fibers are fast-twitch and develop the largest tetanic tension in comparison with the Type I slow-twitch and Type IIa fast-twitch, moderate-tension fibers(Burke, 1994 Kelly and Rubinstein, 1994). Talmadge et al. (1996) found that the IIx isoform, rather than the IIb isoform, is present in cat limb muscles. In cats, therefore, the percentage of MHC Type IIx isoform in extensor muscles should be correlated with jump performance.

The lateral gastrocnemius muscle was chosen for fiber type analysis because it is known to be activated during the cat jump takeoff period(Smith et al., 1977 Abraham and Loeb, 1985) and is known to contain all three MHC types. The most predominant is the Type IIx isoform mean fiber type percentages reported for cats are between 66% and 72%(Braund et al., 1995 Talmadge et. al., 1996). In this study, the lateral gastrocnemius muscles from each cat were prepared for electrophoretic separation in the following manner: the middle one-third,cross-sectional portion of each muscle was dissected, quick-frozen in liquid nitrogen, and smashed into smaller pieces with a hammer. These pieces were then immersed in more liquid nitrogen and ground into a fine powder with mortar and pestle. Muscle powder was added to chilled rigor buffer solution (5 mmol l -1 KCl, 2 mmol l -1 EGTA, 2 mmol l -1 MgCl2, 2 mmol l -1 NaN3, pH 7.2) to produce a final concentration of approximately 0.3 mg myofibrillar protein ml -1 . This protein solution was added to urea—thiourea sample buffer (8 mol l -1 urea, 2 mol l -1 thiourea, 0.05 mol l -1 Tris, pH 6.8), 75 mmol l -1 DTT (dithiothreitol), 3%SDS (sodium dodecyl sulfate) and 0.05% bromophenol blue to produce a final concentration of approximately 0.15 μg myofibrillar proteinμl -1 . Samples were boiled at 100°C for 3 min and stored at-70°C.

The three MHC isoforms present in cat skeletal muscle were separated by pulse electrophoresis in SDS-polyacrylamide (SDS-PAGE) gels using a protocol modified from Talmadge and Roy(1993). All gels were run in vertical slab gel units (Hoefer SE 600, Pharmacia Westshore Technologies,Muskegon, MI, USA) using ECPS 3000/150 power supplies (Pharmacia). Gels were 18 cm×16 cm and were 0.75 mm thick. The stacking gel was composed of 4%(w/v) acrylamide, with an acrylamide: N,N′-methylene-bisacrylamide (bis) ratio of 50:1, deionized water, 70 mmol l -1 Tris (pH 6.8), 0.4% (w/v) SDS, 30% (v/v)glycerol, 4.0 mmol l -1 EDTA, 0.04% (w/v) ammonium persulphate (APS)and 0.36% (v/v) TEMED(N,N,N′,N′-tetramethylethylenediamine). The separating gel consisted of 9% (w/v) acrylamide, with bis cross-linking of 1.5% (ratio 67:1), deionized water, 200 mmol l -1 Tris (pH 8.8), 0.4% (w/v) SDS,30% (v/v) glycerol, 100 mmol l -1 glycine, 0.03% APS and 0.15%TEMED. Polymerization of these gels was initiated with the TEMED and APS. The electrode buffer was the same for both upper and lower reservoirs and consisted of 0.38 mol l -1 glycine, 0.05 mol l -1 (w/v)Tris, 0.01% (w/v) SDS and deionized water (pH 8.9 Talmadge and Roy, 1993). The upper buffer was supplemented with 0.2 mmol l -1 DTT immediately before the start of electrophoresis. Gels were run at constant current (13 mA)for 32 h using a pulse unit connected to a Hoefer model SE600. Pulse cycles of 20 s on/off were used, resulting in an overall variation of voltage between 18 mV and 510 mV. Temperature remained constant at 10°C for the duration of the electrophoresis. Gels were stained with silver and scanned with a BioRad Imaging Densitometer (Model GS-670 Pharmacia Westshore Technologies).

MHC isoforms were quantified using Molecular Analyst (version 1.4) software(Pharmacia Westshore Technologies). Relative proportions of each isoform were calculated by dividing the optical density of each individual isoform band by the summed optical density of all three bands within each column (i.e. by the total MHC isoform content within each individual cat). The proportion of each MHC isoform is thus expressed as the percentage that it contributes to the total area of MHC bands (Fauteck and Kandarian, 1995).

Statistical analysis

Linear correlation analyses and paired t-tests were used to compare maximum velocities on days 1 and 2 to assess performance repeatability. Fat mass was calculated as % body fat multiplied by body mass,and lean body mass was calculated as body mass minus fat mass. Significant correlations were found between lean body mass and hind limb length(r=0.709, two-tailed P=0.001), muscle mass(r=0.917, P<0.001) and fat mass (r=0.739, P<0.001). To examine the effects of these three variables independent of body size, `lean' mass residuals were calculated from a linear regression of each variable vs. lean body mass.

Multiple regression analyses were performed to develop a model containing variables that together explain the most variation in TOV. Lean mass residuals for hind limb length, muscle mass and fat mass were entered, together with lean mass and %MHC IIx content, as independent variables. A backwards elimination criterion was then used to eliminate variables that did not explain a significant amount of variation. Kinetic energy was calculated using whole body mass and maximum TOVs measured from each individual. Potential energy was calculated using whole body mass and hind limb length. The ratio of potential to kinetic energy was compared with fat mass. All analyses were performed using SPSS versions 8.0 and 11.0.


RESULTS

The anthropometric characteristics for the men and women are listed in Table 1. The subjects varied in age (18–88 yr) and adiposity (BMI 16–48 kg/m 2 ). Sixty-seven percent of the subjects were Caucasian, 17% were African-American, 8% were Asian, and 7% were Hispanic. The men (40 ± 14 yr) and women (43 ± 16 yr) were not different with respect to age (P > 0.05). However, the men were taller, heavier, and had a larger BMI in comparison to the women (P < 0.01 Table 1).

Table 1. Subject characteristics

Values are group means ± SD n, no. of subjects. BMI, body mass index SM, skeletal muscle relative SM, body mass/SM mass. For determination of lower and upper body SM see methods.

* Men significantly greater than women, P < 0.01.


The trouble with visceral fat

Body fat, or adipose tissue, was once regarded as little more than a storage depot for fat blobs waiting passively to be used for energy. But research has shown that fat cells — particularly visceral fat cells — are biologically active. One of the most important developments [since the mid-1990s] is the realization that the fat cell is an endocrine organ, secreting hormones and other molecules that have far-reaching effects on other tissues.

Before researchers recognized that fat acts as an endocrine gland, they thought that the main risk of visceral fat was influencing the production of cholesterol by releasing free fatty acids into the bloodstream and liver. We now know that there's far more to the story. Researchers have identified a host of chemicals that link visceral fat to a surprisingly wide variety of diseases.

Subcutaneous fat produces a higher proportion of beneficial molecules, and visceral fat a higher proportion of molecules with potentially deleterious health effects. Visceral fat makes more of the proteins called cytokines, which can trigger low-level inflammation, a risk factor for heart disease and other chronic conditions. It also produces a precursor to angiotensin, a protein that causes blood vessels to constrict and blood pressure to rise.

Gut check

A tape measure is your best home option for keeping tabs on visceral fat. Measure your waistline at the level of the navel — not at the narrowest part of the torso — and always measure in the same place. (According to official guidelines, the bottom of the tape measure should be level with the top of the right hip bone, or ilium — see the illustration — at the point where the ilium intersects a line dropped vertically from the center of the armpit.) Don't suck in your gut or pull the tape tight enough to compress the area. In women, a waist circumference of 35 inches or larger is generally considered a sign of excess visceral fat, but that may not apply if your overall body size is large. Rather than focus on a single reading or absolute cut-off, keep an eye on whether your waist is growing (are your pants getting snug at the waist?). That should give you a good idea of whether you're gaining unhealthy visceral fat.


Gene therapy in mice builds muscle, reduces fat

Researchers at Washington University School of Medicine in St. Louis found that gene therapy in mice helped build strength and significant muscle mass quickly, while reducing the severity of osteoarthritis. The gene therapy also prevented obesity, even when the mice were fed a high-fat diet.

Exercise and physical therapy often are recommended to help people who have arthritis. Both can strengthen muscle — a benefit that also can reduce joint pain. But building muscle mass and strength can take many months and be difficult in the face of joint pain from osteoarthritis, particularly for older people who are overweight. A new study in mice at Washington University School of Medicine in St. Louis, however, suggests gene therapy one day may help those patients.

The research shows that gene therapy helped build significant muscle mass quickly and reduced the severity of osteoarthritis in the mice, even though they didn’t exercise more. The therapy also staved off obesity, even when the mice ate an extremely high-fat diet.

The study is published online May 8 in the journal Science Advances.

“Obesity is the most common risk factor for osteoarthritis,” said senior investigator Farshid Guilak, PhD, the Mildred B. Simon Research Professor of Orthopaedic Surgery and director of research at Shriners Hospitals for Children — St. Louis. “Being overweight can hinder a person’s ability to exercise and benefit fully from physical therapy. We’ve identified here a way to use gene therapy to build muscle quickly. It had a profound effect in the mice and kept their weight in check, suggesting a similar approach may be effective against arthritis, particularly in cases of morbid obesity.”

With the paper’s first author, Ruhang Tang, PhD, a senior scientist in Guilak’s laboratory, Guilak and his research team gave 8-week-old mice a single injection each of a virus carrying a gene called follistatin. The gene works to block the activity of a protein in muscle that keeps muscle growth in check. This enabled the mice to gain significant muscle mass without exercising more than usual.

Even without additional exercise, and while continuing to eat a high-fat diet, the muscle mass of these “super mice” more than doubled, and their strength nearly doubled, too. The mice also had less cartilage damage related to osteoarthritis, lower numbers of inflammatory cells and proteins in their joints, fewer metabolic problems, and healthier hearts and blood vessels than littermates that did not receive the gene therapy. The mice also were significantly less sensitive to pain.

One worry was that some of the muscle growth prompted by the gene therapy might turn out to be harmful. The heart, for example, is a muscle, and a condition called cardiac hypertrophy, in which the heart’s walls thicken, is not a good thing. But in these mice, heart function actually improved, as did cardiovascular health in general.

Longer-term studies will be needed to determine the safety of this type of gene therapy. But, if safe, the strategy could be particularly beneficial for patients with conditions such as muscular dystrophy that make it difficult to build new muscle.

In the meantime, Guilak, who also co-directs the Washington University Center for Regenerative Medicine and is a professor of biomedical engineering and of developmental biology, said more traditional methods of muscle strengthening, such as lifting weights or physical therapy, remain the first line of treatment for patients with osteoarthritis.

“Something like this could take years to develop, but we’re excited about its prospects for reducing joint damage related to osteoarthritis, as well as possibly being useful in extreme cases of obesity,” he said.

Tang R, Harasymowicz NS, Wu CL, Collins KH, Choi YR, Oswald SJ, Guilak F. Gene therapy for follistatin mitigates systemic metabolic inflammation and post-traumatic arthritis in high-fat diet-induced obesity. Science Advances, published online May 8, 2020.

This work was supported by the Shriners’ Hospitals for Children, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Institute on Aging and the Office of the Director of the National Institutes of Health (NIH). Grant numbers AR50245, AR48852, AG15768, AR48182, AG 46927, AR073752, OD10707, AR060719, AR057235. Additional funding was provided by the Arthritis Foundation and the Nancy Taylor Foundation for Chronic Diseases.


Methods

PubMed, MEDLINE, SPORTDiscus and CINAHL electronic databases were searched online. Each author was assigned a portion of the manuscript to write specific to their area(s) of expertise. Authors performed searches for key words associated with their portion(s) of the manuscript calories and macronutrients, nutrient timing and meal frequency, dietary supplementation, psychosocial issues and “peak week” were the selected topics. The publications obtained were carefully screened for studies that included healthy humans or humans in a caloric deficit. Long-term human studies focusing on hypertrophy and body fat loss were preferentially selected however, acute studies and/or studies using animal models were selected in the absence of adequate long-term human studies. In addition, author names and reference lists were used for further search of the selected papers for related references. As this review is intended to be an evidence-based guide and the available data relevant to natural bodybuilding is extremely limited, a narrative review style was chosen.

Nutrition

Calories and macronutrients

Competitive bodybuilders traditionally follow two to four month diets in which calories are decreased and energy expenditure is increased to become as lean as possible [2-6]. In addition to fat loss, muscle maintenance is of primary concern during this period. To this end, optimal caloric intakes, deficits and macronutrient combinations should be followed while matching the changing needs that occur during competition preparation.

Caloric intake for competition

To create weight loss, more energy must be expended than consumed. This can be accomplished by increasing caloric expenditure while reducing caloric intake. The size of this caloric deficit and the length of time it is maintained will determine how much weight is lost. Every pound of pure body fat that is metabolized yields approximately 3500 kcals, thus a daily caloric deficit of 500 kcals theoretically results in fat loss of approximately one pound per week if the weight loss comes entirely from body fat [7]. However, a static mathematical model does not represent the dynamic physiological adaptations that occur in response to an imposed energy deficit [8]. Metabolic adaptation to dieting has been studied in overweight populations and when observed, reductions in energy expenditure amount to as little as 79 kcal/d [9], to as much as 504 kcal/d beyond what is predicted from weight loss [10]. Metabolic adaptations to bodybuilding contest preparation have not been studied however non-overweight men who consumed 50% of their maintenance caloric intake for 24 weeks and lost one fourth of their body mass experienced a 40% reduction in their baseline energy expenditure. Of that 40% reduction 25% was due to weight loss, while metabolic adaptation accounted for the remaining 15% [11]. Therefore, it should be expected that the caloric intake at which one begins their preparation will likely need to be adjusted over time as body mass decreases and metabolic adaptation occurs. A complete review of metabolic adaptation to dieting in athletes is beyond the scope of this review. However, coaches and competitors are encouraged to read the recent review on this topic by Trexler et al. [12] which covers not only the physiology of metabolic adaptation, but also potential methods to mitigate its negative effects.

In determining an appropriate caloric intake, it should be noted that the tissue lost during the course of an energy deficit is influenced by the size of the energy deficit. While greater deficits yield faster weight loss, the percentage of weight loss coming from lean body mass (LBM) tends to increase as the size of the deficit increases [7,13-15]. In studies of weight loss rates, weekly losses of 1 kg compared to 0.5 kg over 4 weeks resulted in a 5% decrease in bench press strength and a 30% greater reduction in testosterone levels in strength training women [16]. Weekly weight loss rates of 1.4% of bodyweight compared to 0.7% in athletes during caloric restriction lasting four to eleven weeks resulted in reductions of fat mass of 21% in the faster weight loss group and 31% in the slower loss group. In addition, LBM increased on average by 2.1% in the slower loss group while remaining unchanged in the faster loss group. Worthy of note, small amounts of LBM were lost among leaner subjects in the faster loss group [13].

Therefore, weight loss rates that are more gradual may be superior for LBM retention. At a loss rate of 0.5 kg per week (assuming a majority of weight lost is fat mass), a 70 kg athlete at 13% body fat would need to be no more than 6 kg to 7 kg over their contest weight in order to achieve the lowest body fat percentages recorded in competitive bodybuilders following a traditional three month preparation [4,6,17-20]. If a competitor is not this lean at the start of the preparation, faster weight loss will be required which may carry a greater risk for LBM loss.

In a study of bodybuilders during the twelve weeks before competition, male competitors reduced their caloric intake significantly during the latter half and subsequently lost the greatest amount of LBM in the final three weeks [21]. Therefore, diets longer than two to four months yielding weight loss of approximately 0.5 to 1% of bodyweight weekly may be superior for LBM retention compared to shorter or more aggressive diets. Ample time should be allotted to lose body fat to avoid an aggressive deficit and the length of preparation should be tailored to the competitor those leaner dieting for shorter periods than those with higher body fat percentages. It must also be taken into consideration that the leaner the competitor becomes the greater the risk for LBM loss [14,15]. As the availability of adipose tissue declines the likelihood of muscle loss increases, thus it may be best to pursue a more gradual approach to weight loss towards the end of the preparation diet compared to the beginning to avoid LBM loss.

Determining macronutrient intake

Protein

Adequate protein consumption during contest preparation is required to support maintenance of LBM. Athletes require higher protein intakes to support increased activity and strength athletes benefit from higher intakes to support growth of LBM [5,22-28]. Some researchers suggest these requirements increase further when athletes undergo energy restriction [13,16,22,28-33]. Furthermore, there is evidence that protein requirements are higher for leaner individuals in comparison to those with higher body fat percentages [7,33,34].

The collective agreement among reviewers is that a protein intake of 1.2-2.2 g/kg is sufficient to allow adaptation to training for athletes whom are at or above their energy needs [23-28,35-38]. However, bodybuilders during their contest preparation period typically perform resistance and cardiovascular training, restrict calories and achieve very lean conditions [2-6,17-21]. Each of these factors increases protein requirements and when compounded may further increase protein needs [33]. Therefore, optimal protein intakes for bodybuilders during contest preparation may be significantly higher than existing recommendations.

In support of this notion, Butterfield et al. [22] found that male athletes running five to 10 miles per day during a slight caloric deficit were in a significant negative nitrogen balance despite consuming 2 g/kg of protein daily. Celejowa et al. [39] showed that five out of 10 competitive weight lifters achieved a negative nitrogen balance over the course of a training camp while consuming an average protein intake of 2 g/kg. Out of these five, as many as three were in a caloric deficit. The authors concluded that a protein intake of 2𠄲.2 g/kg under these conditions only allows for a small margin of error before nitrogen losses occur.

Walberg et al. [32] examined the effects of two energy restricted isocaloric diets of differing protein intakes in 19 lean (9.1-16.7% body fat), male, non-competitive body builders. One group consumed a protein intake of 0.8 g/kg and higher carbohydrates, while the other consumed 1.6 g/kg of protein with lower carbohydrates. The length of the intervention was only one week, but nonetheless nitrogen losses occurred only in the lower protein group and LBM decreased by a mean of 2.7 kg in the 0.8 g/kg protein group and by a mean of 1.4 kg in the 1.6 g/kg protein group. While the high protein group mitigated LBM losses compared to the low protein group, they were not eliminated.

A recent study by Mettler et al. [29] employed the same basic methodology as Walberg et al. [32]. However, one group consumed a protein intake of 1 g/kg, while the other consumed 2.3 g/kg. The high-protein group lost significantly less LBM (0.3 kg) over the course of the two week intervention compared to the low-protein group (1.6 kg). Unlike Walberg et al. [32] calorie balance between diets was maintained by reducing dietary fat as opposed to carbohydrate to allow for the increase in protein.

While it appears that the 2.3 g/kg protein intervention in Mettler et al. [29] was superior for maintaining LBM compared to 1.6 g/kg in Walberg et al. [32] a recent study by Pasiakos et al. [40] found a trend towards the opposite. In this study, a non-significant trend of greater LBM retention occurred when subjects consumed 1.6 g/kg of protein compared to 2.4 g/kg of protein. However, the participants were intentionally prescribed low volume, low intensity resistance training "to minimize the potential of an unaccustomed, anabolic stimulus influencing study outcome measures". Thus, the non-anabolic nature of the training may not have increased the participants’ protein requirements to the same degree as the participants in Mettler et al. [29] or to what would be expected among competitive bodybuilders.

Maestu et al. [6] did not observe a significant loss of LBM in a group of drug free bodybuilders consuming 2.5-2.6 g/kg of protein during the 11 weeks prior to competition. These results when considered alongside the works by Walberg et al. [32] and Mettler et al. [29] imply that the higher the protein intake, the lower the chance for LBM loss. However, it should be noted that this study did not include a low protein control and not all studies show a linear increase in LBM preservation with increases in protein [40]. Furthermore, two subjects did lose significant amounts of LBM (1.5 kg and 1.8 kg), and the authors noted that these specific bodybuilders were among the leanest of the subjects. These two subjects lost the majority of their LBM (approximately 1 kg) during the latter half of the intervention as their percentage of calories from protein increased from 28% to 32-33% by the end of the study. The group as a whole progressively decreased their calories by reducing all three macronutrients throughout the investigation. Thus, the two subjects uniquely increased their proportion of protein, possibly reducing fat and carbohydrate to the point of detriment [6]. That said it is also plausible that the lost LBM seen by these two subjects was necessary in order to achieve their low levels of body fat. It is unknown whether or not the lost LBM influenced their competitive outcome and it is possible that had the competitors not been as lean, they may have retained more LBM but also not have placed as well.

In a review by Phillips and Van Loon [28], it is suggested that a protein intake of 1.8-2.7 g/kg for athletes training in hypocaloric conditions may be optimal. While this is one of the only recommendations existing that targets athletes during caloric restriction, this recommendation is not given with consideration to bodybuilders performing concurrent endurance and resistance training at very low levels of body fat. However, the recently published systematic review by Helms et al. [33] on protein intakes in resistance-trained, lean athletes during caloric restriction suggests a range of 2.3-3.1 g/kg of LBM, which may be more appropriate for bodybuilding. Moreover, the authors suggest that the lower the body fat of the individual, the greater the imposed caloric deficit and when the primary goal is to retain LBM, the higher the protein intake (within the range of 2.3-3.1 g/kg of LBM) should be.

Carbohydrate

High carbohydrate diets are typically thought to be the athletic performance standard. However, like protein, carbohydrate intake needs to be customized to the individual. Inadequate carbohydrate can impair strength training [41] and consuming adequate carbohydrate prior to training can reduce glycogen depletion [42] and may therefore enhance performance.

While it is true that resistance training utilizes glycogen as its main fuel source [43], total caloric expenditure of strength athletes is less than that of mixed sport and endurance athletes. Thus, authors of a recent review recommend that carbohydrate intakes for strength sports, including bodybuilding, be between 4𠄷 g/kg depending on the phase of training [26]. However, in the specific case of a bodybuilder in contest preparation, achieving the necessary caloric deficit while consuming adequate protein and fat would likely not allow consumption at the higher end of this recommendation.

Satiety and fat loss generally improve with lower carbohydrate diets specifically with higher protein to carbohydrate ratios [44-49]. In terms of performance and health, low carbohydrate diets are not necessarily as detrimental as typically espoused [50]. In a recent review, it was recommended for strength athletes training in a calorically restricted state to reduce carbohydrate content while increasing protein to maximize fat oxidation and preserve LBM [28]. However, the optimal reduction of carbohydrate and point at which carbohydrate reduction becomes detrimental likely needs to be determined individually.

One comparison of two isocaloric, energy restricted diets in bodybuilders showed that a diet that provided adequate carbohydrate at the expense of protein (1 g/kg) resulted in greater LBM losses compared to a diet that increased protein (1.6 g/kg) through a reduction of carbohydrate [32]. However, muscular endurance was degraded in the lower carbohydrate group. In a study of athletes taking in the same amount of protein (1.6 g/kg) during weight loss, performance decrements and LBM losses were avoided when adequate carbohydrate was maintained and dietary fat was lowered [13]. Mettler, et al. [29] also found that a caloric reduction coming from dietary fat while maintaining adequate carbohydrate intake and increasing protein to 2.3 g/kg maintained performance and almost completely eliminated LBM losses in resistance trained subjects. Finally, in Pasiakos et al. [40] participants undergoing an equal calorie deficit and consuming the same amount of protein as those observed in Mettler et al. [29] lost three times the amount of LBM over the same time period (0.9 kg in the first two weeks of energy restriction observed by Pasiakos versus 0.3 kg observed by Mettler). One key difference between these studies was the highest protein group in Mettler et al. [29] consumed a 51% carbohydrate diet while the comparable group in Pasiakos et al. [40] consumed a 27% carbohydrate diet. While performance was not measured, the participants in Pasiakos et al. [40] performing sets exclusively of 15 repetitions very likely would have experienced decrements in performance due to this carbohydrate intake level [32]. The difference in training protocols or a nutritionally mediated decrement in training performance could have either or both been components that lead to the greater losses of LBM observed by Pasiakos et al. [40].

While it appears low carbohydrate, high protein diets can be effective for weight loss, a practical carbohydrate threshold appears to exist where further reductions negatively impact performance and put one at risk for LBM losses. In support of this notion, researchers studying bodybuilders during the final 11 weeks of contest preparation concluded that had they increased carbohydrate during the final weeks of their diet they may have mitigated metabolic and hormonal adaptations that were associated with reductions in LBM [6].

Therefore, once a competitor has reached or has nearly reached the desired level of leanness, it may be a viable strategy to reduce the caloric deficit by an increase in carbohydrate. For example, if a competitor has reached competition body fat levels (lacking any visible subcutaneous fat) and is losing half a kilogram per week (approximately a 500 kcals caloric deficit), carbohydrate could be increased by 25-50 g, thereby reducing the caloric deficit by 100-200 kcals in an effort to maintain performance and LBM. However, it should be noted that like losses of LBM, decrements in performance may not affect the competitive outcome for a bodybuilder. It is possible that competitors who reach the leanest condition may experience unavoidable drops in performance.

The importance of carbohydrate and protein in sports nutrition is often emphasized over that of dietary fat. Subsequently, recommendations typically focus on maintaining adequate fat intake while emphasizing carbohydrate to fuel performance and protein to build and repair LBM. However, there is evidence that dietary fat influences anabolic hormone concentrations which may be of interest to bodybuilders attempting to maintain LBM while dieting [5,26,51,52].

Reductions in the percentage of dietary fat in isocaloric diets from approximately 40% to 20% has resulted in modest, but significant, reductions in testosterone levels [53,54]. However, distinguishing the effects of reducing total dietary fat on hormonal levels from changes in caloric intake and percentages of saturated and unsaturated fatty acids in the diet is difficult [51,52,55]. In a study by Volek et al. [51], correlations were found between testosterone levels, macronutrient ratios, types of lipids, and total dietary fat, illustrating a complex interaction of variables. In a similar study of resistance trained males, correlations were found between testosterone, protein, fat and saturated fat which lead the researchers to conclude that diets too low in fat or too high in protein might impair the hormonal response to training [52].

Competing bodybuilders must make an obligatory caloric reduction. If a reduction in fat is utilized, it may be possible to attenuate a drop in testosterone by maintaining adequate consumption of saturated fat [5]. However, a drop in testosterone does not equate to a reduction in LBM. In direct studies of resistance trained athletes undergoing calorically restricted high protein diets, low fat interventions that maintain carbohydrate levels [13,29] appear to be more effective at preventing LBM loses than lower carbohydrate, higher fat approaches [32,40]. These results might indicate that attempting to maintain resistance training performance with higher carbohydrate intakes is more effective for LBM retention than attempting to maintain testosterone levels with higher fat intakes.

Body composition and caloric restriction may play greater roles in influencing testosterone levels that fat intake. During starvation, a reduction in testosterone occurs in normal weight, but not obese, males [56]. In addition, rate of weight loss may influence testosterone levels. Weekly target weight loss rates of 1 kg resulted in a 30% reduction in testosterone compared to target weight loss rates of 0.5 kg per week in resistance trained women of normal weight [16]. Additionally, an initial drop in testosterone occurred in the first six weeks of contest preparation in a group of drug free bodybuilders despite various macronutrient percentages [6]. Finally, in a one year case study of a natural competitive bodybuilder, testosterone levels fell to one fourth their baseline values three months into the six month preparation period. Levels then fully recovered three months into the six month recovery period. Testosterone did not decline further after the initial drop at the three month mark despite a slight decrease in fat intake from 27% to 25% of calories at the six month mark. Furthermore, the quadrupling of testosterone during the recovery period from its suppressed state back to baseline was accompanied by a 10 kg increase in body mass and a 1000 kcal increase in caloric intake. However, there was only a minor increase in calories from fat (percentage of calories from fat during recovery was between (30 and 35%) [57]. Finally, these testosterone changes in men appear mostly related to energy availability (body fat content and energy balance), and not surprisingly low-levels of sustained energy availability are also the proposed cause of the hormonal disturbance 𠇊thletic amenorrhea” in women [58]. Thus, the collective data indicates that when extremely lean body compositions are attained through extended, relatively aggressive dieting, the caloric deficit and loss of body fat itself may have a greater impact on testosterone than the percentage of calories coming from dietary fat.

While cogent arguments for fat intakes between 20 to 30% of calories have been made to optimize testosterone levels in strength athletes [59], in some cases this intake may be unrealistic in the context of caloric restriction without compromising sufficient protein or carbohydrate intakes. While dieting, low carbohydrate diets may degrade performance [32] and lead to lowered insulin and IGF-1 which appear to be more closely correlated to LBM preservation than testosterone [6]. Thus, a lower end fat intake between 15-20% of calories, which has been previously recommended for bodybuilders [5], can be deemed appropriate if higher percentages would reduce carbohydrate or protein below ideal ranges.

Ketogenic diets and individual variability

Some bodybuilders do use very-low carbohydrate, "ketogenic diets" for contest preparation [60,61]. While these diets have not been sufficiently studied in bodybuilders, some study of ketogenic diets has occurred in resistance trained populations. In an examination of the effects of a 1 week ketogenic diet (5.4% of calories from carbohydrate) in subjects with at least 2 years of resistance training experience, Sawyer et al. [62] observed slight decreases in body fat among female participants and maintenance or slight increases in measures of strength and power among both male and female participants. However, it is difficult to draw conclusions due to the very short term nature of this study and due to an ad libitum implementation of the ketogenic diet. As implemented in this study, besides a reduction in carbohydrate and an increase in dietary fat, the ketogenic diet resulted in an average reduction of 381 calories per day and an increase of 56 g of protein per day compared to the participants’ habitual diets. Thus, it is unclear whether the improvements in body composition and performance can be attributed to the low-carbohydrate and high-fat nature of the diets or rather a decrease in calories and an increase in protein. At least with regards to weight loss, previous research indicates that the often concomitant increase in protein observed in very low carbohydrate diets may actually be the key to their success [63].

The only research on strength athletes following ketogenic diets for longer periods is a study of gymnasts in which they were observed to maintain strength performance and lose more body fat after 30ꃚys on a ketogenic diet in comparison to 30ꃚys on a traditional western diet [64]. However, this study's sample size was limited (n =𠂘) and it was not a controlled study of an intentional fat-loss phase such as seen among bodybuilders during competition preparation. Therefore, more study is needed in resistance trained populations and bodybuilders before definitive recommendations can be made to support ketogenic diets.

However, the research that does exist challenges traditional views on carbohydrate and anaerobic performance. Despite the common belief that carbohydrate is the sole fuel source for weight training, intramuscular triglyceride is used during short term heavy resistance training [65] and likely becomes an increasingly viable fuel source for those adapted to high-fat low-carbohydrate diets. While some might suggest that this implies a ketogenic diet could be a viable option for contest preparation, a trend of decreased performance and impaired maintenance of FFM is associated with lower carbohydrate intakes in the majority of studies included in this review.

While it is our contention that the majority of the evidence indicates that very-low carbohydrate diets should be avoided for contest preparation (at least until more research is performed), it must be noted that there is a high degree of variability in the way that individuals respond to diets. Carbohydrate and fat utilization as a percentage of energy expenditure at rest and various intensities has as much as a four-fold difference between individual athletes which is influenced by muscle fiber-composition, diet, age, training, glycogen levels and genetics [66]. Additionally, individuals that are more insulin sensitive may lose more weight with higher-carbohydrate low-fat diets while those more insulin resistant may lose more weight with lower-carbohydrate higher-fat diets [67].

Due to this individual variability, some popular commercial bodybuilding literature suggests that somatotype and/or body fat distribution should be individually assessed as a way of determining macronutrient ratios. However, there is no evidence of any relationships with bone structure or regional subcutaneous fat distribution with any response to specific macronutrient ratios in bodybuilders or athletic populations. Bodybuilders, like others athletes, most likely operate best on balanced macronutrient intakes tailored to the energy demands of their sport [68].

In conclusion, while the majority of competitors will respond best to the fat and carbohydrate guidelines we propose, the occasional competitor will undoubtedly respond better to a diet that falls outside of these suggested ranges. Careful monitoring over the course of a competitive career is required to determine the optimal macronutrient ratio for pre-contest dieting.

Macronutrient recommendations summary

After caloric intake is established based on the time frame before competition [69], body composition of the athlete [14,15,34], and keeping the deficit modest to avoid LBM losses [13,16], macronutrients can be determined within this caloric allotment. Table  1 provides an overview of these recommendations.

Table 1

Dietary recommendations for bodybuilding contest preparation

Diet componentRecommendation
Protein (g/kg of LBM) 2.3-3.1 [33]
Fat (% of total calories) 15-30% [5,59]
Carbohydrate (% of total calories) remaining
Weekly weight loss (% of body weight)0.5-1% [13,16]

If training performance degrades it may prove beneficial to decrease the percentage of calories from dietary fat within these ranges in favor of a greater proportion of carbohydrate. Finally, while outside of the norm, some competitors may find that they respond better to diets that are higher in fat and lower in carbohydrate than recommended in this review. Therefore, monitoring of individual response over a competitive career is suggested.

Nutrient timing

Traditional nutrient timing guidelines are typically based on the needs of endurance athletes. For example, it is common lore that post-exercise carbohydrate must elicit a substantial glycemic and insulinemic response in order to optimize recovery. The origin of this recommendation can be traced back to 1988, when Ivy et al. [70] put fasted subjects through a glycogen-depleting cycling bout and compared the rate of glycogen resynthesis from a carbohydrate solution (2 g/kg) consumed either immediately after, or two hours after the bout. Glycogen storage was 2𠄳 times faster in the immediate condition during four hours post-exercise resulting in greater glycogen storage at four hours.

These findings initiated the faster-is-better post-exercise guideline for carbohydrate. However, complete glycogen resynthesis to pre-trained levels can occur well within 24 hours given sufficient total carbohydrate intake. Jentjens and Jeukendrup [71] suggest that a between-bout period of eight hours or less is grounds for maximally expediting glycogen resynthesis. Therefore, the urgency of glycogen resynthesis is almost an exclusive concern of endurance athletes with multiple glycogen-depleting events separated by only a few hours. Bodybuilders in contest preparation may exceed a single training bout per day (e.g., weight-training in the morning, cardio in the evening). However, bodybuilders do not have the same performance objectives as multi-stage endurance competition, where the same muscle groups are trained to exhaustion in a repeated manner within the same day. Furthermore, resistance training bouts are typically not glycogen-depleting. High-intensity (70-80% of 1 RM), moderate-volume (6𠄹 sets per muscle group) bouts have been seen to reduce glycogen stores by roughly 36-39% [72,73].

A more relevant question to bodybuilding may be whether protein and/or amino acid timing affect LBM maintenance. With little exception [74], acute studies have consistently shown that ingesting protein/essential amino acids and carbohydrate near or during the training bout can increase muscle protein synthesis (MPS) and suppress muscle protein breakdown [75-79]. However, there is a disparity between short- and long-term outcomes in studies examining the effect of nutrient timing on resistance training adaptations.

To-date, only a minority of chronic studies have shown that specific timing of nutrients relative to the resistance training bout can affect gains in muscular size and/or strength. Cribb and Hayes [80] found that timing a supplement consisting of 40 g protein, 43 g carbohydrate, and 7 g creatine immediately pre- and post-exercise resulted in greater size and strength gains than positioning the supplement doses away from the training bout. Additionally, Esmarck et al. [81] observed greater hypertrophy in subjects who ingested a supplement (10 g protein, 8 g carbohydrate, 3 g fat) immediately post-exercise than subjects who delayed the supplement 2 hours post-exercise.

In contrast, the majority of chronic studies have not supported the effectiveness of timing nutrients (protein in particular) closely around the training bout. Burk et al. [82], found that a time-divided regimen (two 35 g protein doses consumed at far-off points in the morning and evening away from the afternoon training bout) caused slightly better gains in squat strength and fat-free mass than the time-focused regimen, where the protein supplement doses were consumed in the morning, and then again immediately prior to the resistance training bout. Hoffman et al. [83] found no significant differences in strength gains or body composition when comparing an immediate pre- and post-exercise supplement ingestion (each dose provided 42 g protein) with the supplement ingested distantly separate from each side of the training bout. This lack of effect was attributed to the subjects’ sufficient daily protein consumption combined with their advanced lifting status. Wycherley et al. [84] examined the effects of varying nutrient timing on overweight and obese diabetics. A meal containing 21 g protein consumed immediately before resistance training was compared with its consumption at least two hours after training. No significant differences in weight loss, strength gain, or cardio metabolic risk factor reductions were seen. Most recently, Weisgarber et al. [85] observed no significant effect on muscle mass and strength from consuming whey protein immediately before or throughout resistance training.

It’s important to note that other chronic studies are referred to as nutrient timing studies, but have not matched total protein intake between conditions. These studies examined the effect of additional nutrient content, rather than examining the effect of different temporal placement of nutrients relative to the training bout. Thus, they cannot be considered true timing comparisons. Nevertheless, these studies have yielded inconsistent results. Willoughby et al. [86] found that 10 weeks of resistance training supplemented with 20 g protein and amino acids 1 hour pre- and post-exercise increased strength performance and MPS compared to an energy-matched carbohydrate placebo. Hulmi et al. [87] found that 21 weeks of supplementing 15 g of whey before and after resistance training increased size and altered gene expression favorably towards muscle anabolism in the vastus lateralis. In contrast to the previous 2 studies, Verdijk et al. [88] found no significant effect of 10 g protein timed immediately before and after resistance training over a 12-week period. The authors attributed this lack of effect to an adequate total daily protein intake. Recently, a 12-week trial by Erksine et al. [89] reported a lack of effect of 20 g protein taken pre- and post-exercise compared to placebo.

The disparity of outcomes between the acute and chronic studies could also potentially be due to a longer 𠇊nabolic window” than traditionally thought. Burd and colleagues [90] found that resistance training to failure can cause an increased anabolic response to protein feedings that can last up to 24 hours. Demonstrating the body's drive toward equilibrium, Deldicque et al. [91] observed a greater intramyocellular anabolic response in fasted compared to fed subjects given a post-exercise carbohydrate/protein/leucine mixture. This result suggests that the body is capable of anabolic supercompensation despite the inherently catabolic nature of fasted resistance training. These data, in addition to the previously discussed chronic studies, further support the idea that macronutrient totals by the end of the day may be more important than their temporal placement relative to the training bout.

There are additional factors that might explain the lack of consistent effectiveness of nutrient timing in chronic studies. Training status of the subjects could influence outcomes since novice trainees tend to respond similarly to a wider variety of stimuli. Another possible explanation for the lack of timing effects is the protein dose used, 10� g, which may not be sufficient to elicit a maximal anabolic response. MPS rates have been shown to plateau with a post-exercise dose of roughly 20 g of high-quality protein [92]. However, in subsequent research on older subjects, Yang et al. [93] observed that an even higher post-exercise protein dose (40 g) stimulated MPS to a greater extent than 10 g or 20 g.

In addition to the paucity of studies using ample protein doses, there is a lack of investigation of protein-carbohydrate combinations. Only Cribb and Hayes [80] have compared substantial doses of both protein (40 g) and carbohydrate (43 g) taken immediately surrounding, versus far apart from both sides of the training bout. Nearly double the lean mass gains were seen in the proximally timed compared to the distally timed condition. However, acute studies examining the post-exercise anabolic response elicited by co-ingesting carbohydrate with protein have thus far failed to show significant effects given a sufficient protein dose of approximately 20� g [94,95]. These results concur with previous data indicating that only moderate insulin elevations (15� mU/L) are required to maximize net muscle protein balance in the presence of elevated plasma amino acids [96]. Koopman et al. [97] observed a similar lack of carbohydrate-mediated anabolic effect when protein was administered at 0.3 g/kg/hr in the post-exercise recovery period.

Questions remain about the utility of consuming protein and/or carbohydrate during bodybuilding-oriented training bouts. Since these bouts typically do not resemble endurance bouts lasting 2 hours or more, nutrient consumption during training is not likely to yield any additional performance-enhancing or muscle -sparing benefits if proper pre-workout nutrition is in place. In the exceptional case of resistance training sessions that approach or exceed two hours of exhaustive, continuous work, it might be prudent to employ tactics that maximize endurance capacity while minimizing muscle damage. This would involve approximately 8� g protein co-ingested with 30� g carbohydrate in a 6-8% solution per hour of training [98]. Nutrient timing is an intriguing area of study that focuses on what might clinch the competitive edge. In terms of practical application to resistance training bouts of typical length, Aragon and Schoenfeld [99] recently suggested a protein dose corresponding with 0.4-0.5 g/kg bodyweight consumed at both the pre- and post-exercise periods. However, for objectives relevant to bodybuilding, the current evidence indicates that the global macronutrient composition of the diet is likely the most important nutritional variable related to chronic training adaptations. Figure  1 below provides a continuum of importance with bodybuilding-specific context for nutrient timing.

Continuum of nutrient & supplement timing importance.

Meal frequency

Previous optimal meal frequency studies have lacked structured resistance training protocols. Moreover, there are no studies that specifically examined meal frequency in bodybuilders, let alone during contest preparation conditions. Despite this limitation, the available research has consistently refuted the popular belief that a grazing pattern (smaller, more frequent meals) raises energy expenditure compared to a gorging pattern (larger, less frequent meals). Disparate feeding patterns ranging from two to seven meals per day have been compared in tightly controlled studies using metabolic chambers, and no significant differences in 24-hour thermogenesis have been detected [100,101]. It should be noted that irregular feeding patterns across the week, as opposed to maintaining a stable daily frequency, has been shown to decrease post-prandial thermogenesis [102] and adversely affect insulin sensitivity and blood lipid profile [103]. However, relevance of the latter findings might be limited to sedentary populations, since regular exercise is well-established in its ability to improve insulin sensitivity and blood lipids.

Bodybuilders typically employ a higher meal frequency in an attempt to optimize fat loss and muscle preservation. However, the majority of chronic experimental studies have failed to show that different meal frequencies have different influences on bodyweight or body composition [104-108]. Of particular interest is the research examining the latter, since the preservation of muscle mass during fat loss is a paramount concern in the pre-contest phase. A recent review by Varady [109] examined 11 daily caloric restriction (CR) studies and 7 intermittent calorie restriction (ICR) studies. CR involved a linear consumption of 15-60% of baseline needs every day, while ICR alternated ad libitum �’ days with �st’ days involving partial or total food intake restriction. It was concluded that although both types have similar effects on total bodyweight reduction, ICR has thus far been more effective for retaining lean mass. Three of the ICR studies showed no significant decrease in LBM, while all of the CR studies showed decreased LBM. However, the majority of the ICR trials used bioelectrical impedance analysis (BIA) to measure body composition, while the majority of CR studies used dual X-ray absorptiometry (DXA) or magnetic resonance imaging (MRI). These methods have been shown to have greater accuracy than BIA [110-112], so the results of Varady’s [109] analysis should be interpreted with caution. Along these lines, Stote et al. [113] found that compared to three meals per day, one meal per day caused slightly more weight and fat loss. Curiously, the one meal per day group also showed a slight gain in lean mass, but this could have been due to the inherent error in BIA for body composition assessment.

To-date, only two experimental studies have used trained, athletic subjects. Iwao et al. [114] found that boxers consuming six meals a day lost less LBM and showed lower molecular measures of muscle catabolism than the same diet consumed in two meals per day. However, limitations to this study included short trial duration, subpar assessment methods, a small sample size, and a 1200 kcal diet which was artificially low compared to what this population would typically carry out in the long-term. It is also important to note that protein intake, at 20% of total kcal, amounted to 60 g/day which translates to slightly under 1.0 g/kg. To illustrate the inadequacy of this dose, Mettler et al. [29] showed that protein as high as 2.3 g/kg and energy intake averaging 2022 kcal was still not enough to completely prevent LBM loss in athletes under hypocaloric conditions. The other experimental study using athletic subjects was by Benardot et al. [115], who compared the effects of adding three 250 kcal between-meal snacks with the addition of a noncaloric placebo. A significant increase in anaerobic power and lean mass was seen in the snacking group, with no such improvements seen in the placebo group. However, it is not possible to determine if the superior results were the result of an increased meal frequency or increased caloric intake.

A relatively recent concept with potential application to meal frequency is that a certain minimum dose of leucine is required in order to stimulate muscle protein synthesis. Norton and Wilson [116] suggested that this threshold dose is approximately 0.05 g/kg, or roughly 3 g leucine per meal to saturate the mTOR signaling pathway and trigger MPS. A related concept is that MPS can diminish, or become 'refractory' if amino acids are held at a constant elevation. Evidence of the refractory phenomenon was shown by Bohé et al. [117], who elevated plasma amino acid levels in humans and observed that MPS peaked at the 2-hour mark, and rapidly declined thereafter despite continually elevated blood amino acid levels. For the goal of maximizing the anabolic response, the potential application of these data would be to avoid spacing meals too closely together. In addition, an attempt would be made to reach the leucine threshold with each meal, which in practical terms would be to consume at least 30� g high-quality protein per meal. In relative agreement, a recent review by Phillips and Van Loon [28] recommends consuming one's daily protein requirement over the course of three to four isonitrogenous meals per day in order to maximize the acute anabolic response per meal, and thus the rate of muscle gain.

It is important to note that the leucine threshold and the refractory nature of MPS are not based on human feeding studies that measure concrete outcomes over the long-term. These ideas are largely based on mechanistic studies whose data was derived via steady intravenous infusion of amino acids [117,118]. Long-term studies are needed to determine if the refractory nature of MPS seen in acute infusion data would have any real impact on the gain or preservation of LBM at various meal frequencies.

Munster and Saris [119] recently shed further light on what might be optimal in the context of pre-contest dieting. Lean, healthy subjects underwent 36-hour periods in a respiration chamber. Interestingly, three meals per day resulted in higher protein oxidation and RMR, along with lower overall blood glucose concentrations than an isoenergetic diet composed of 14 meals per day. The lower glucose AUC observed in this study is in agreement with previous research by Holmstrup et al. [120], who reported lower 12-hour glucose concentrations as a result of consuming three high-carbohydrate meals compared to the equivalent distributed over the course of six meals. Another interesting finding by Munster and Saris [119] was lower hunger and higher satiety ratings in the lower meal frequency condition. This finding concurred with previous work by Leidy et al. [121], who compared varying protein levels consumed across either three or six meals per day. Predictably, the higher-protein level (25% vs. 14%) promoted greater satiety. Interestingly, the higher meal frequency led to lower daily fullness ratings regardless of protein level. Meal frequency had no significant impact on ghrelin levels, regardless of protein intake. PYY, a gut peptide associated with satiety, was 9% lower in the higher meal frequency condition. However, Arciero et al. [122] recently found that six meals per day in a high-protein condition (35% of total energy) were superior to three meals with a high-protein or traditional protein intake (15% of total energy) for improving body composition in overweight subjects. The discrepancy between Leidy et al’s short-term effects and Arciero’s chronic effects warrants further study, preferably in subjects undergoing progressive resistance training.

Other common meal frequencies (i.e., 4 or 5 meals per day) have eluded scientific investigation until very recently. Adechian et al. [123] compared whey versus casein consumed in either a 'pulse' meal pattern (8/80/4/8%) or a 'spread' pattern (25/25/25/25%) over a six week hypocaloric period. No significant changes were seen in body composition between conditions. These outcomes challenge Phillips and Van Loon's recommendation for protein-rich meals throughout the day to be isonitrogenous (40). Moore et al. [124] compared evenly spaced distributions of two, four, and eight meals consumed after a fasted, acute bout of bilateral knee extension. A trend toward a small and moderate increase in net protein balance was seen in the four meal and eight meal conditions, respectively, compared to the two meal condition. Subsequent work by Areta et al. [125] using the same dosing comparison found that the four meal treatment (20 g protein per meal) caused the greatest increase in myofibrillar protein synthesis. A limitation of both of the previous studies was the absence of other macronutrients (aside from protein in whey) consumed during the 12-hour postexercise period. This leaves open questions about how a real-world scenario with mixed meals might have altered the outcomes. Furthermore, these short-term responses lack corroboration in chronic trials measuring body composition and/or exercise performance outcomes.

The evidence collectively suggests that extreme lows or highs in meal frequency have the potential to threaten lean mass preservation and hunger control during bodybuilding contest preparation. However, the functional impact of differences in meal frequency at moderate ranges (e.g., 3𠄶 meals per day containing a minimum of 20 g protein each) are likely to be negligible in the context of a sound training program and properly targeted total daily macronutrition.

Nutritional supplementation

When preparing for a bodybuilding contest, a competitor primarily focuses on resistance training, nutrition, and cardiovascular training however, supplements may be used to further augment preparation. This section will discuss the scientific evidence behind several of the most commonly used supplements by bodybuilders. However, natural bodybuilding federations have extensive banned substance lists [126] therefore, banned substances will be omitted from this discussion. It should be noted that there are considerably more supplements that are used by bodybuilders and sold on the market. However, an exhaustive review of all of the supplements commonly used by bodybuilders that often lack supporting data is beyond the scope of this paper. In addition, we have omitted discussion of protein supplements because they are predominantly used in the same way that whole food protein sources are used to reach macronutrient targets however, interested readers are encouraged to reference the ISSN position stand on protein and exercise [127].

Creatine

Creatine monohydrate (CM) has been called the most ergogenic and safe supplement that is legally available [128]. Supplementation of healthy adults has not resulted in any reported adverse effects or changes in liver or kidney function [129]. Numerous studies have found significantly increased muscle size and strength when CM was added to a strength training program [130-134]. In many of these studies, 1-2 kg increases in total body mass were observed after CM loading of 20 g/day for 4� days [135]. However, the loading phase may not be necessary. Loading 20 g CM per day has been shown to increase muscle total creatine by approximately 20 percent and this level of muscle creatine was maintained with 2 g CM daily for 30ꃚys [136]. However, the same study also observed a 20 percent increase in muscle creatine when 3 g CM was supplemented daily for 28ꃚys, indicating the loading phase may not be necessary to increase muscle creatine concentrations.

Recently, alternative forms of creatine, such as creatine ethyl ester (CEE) and Kre Alkalyn (KA) have been marketed as superior forms of creatine to CM however, as of this time these claims have not been supported by scientific studies. Tallon and Child [137,138] found that a greater portion of CEE and KA are degraded in the stomach than CM. Additionally, recent investigations have shown that 28� days of CEE or KA supplementation did not increase muscle creatine concentrations more than CM [139,140]. Thus, it appears that CM may be the most effective form of creatine.

Beta-alanine

Beta-alanine (BA) is becoming an increasingly popular supplement among bodybuilders. Once consumed, BA enters the circulation and is up-taken by skeletal muscle where it is used to synthesize carnosine, a pH buffer in muscle that is particularly important during anaerobic exercise such as sprinting or weightlifting [141]. Indeed, consumption of 6.4 g BA daily for four weeks has been shown to increase muscle carnosine levels by 64.2% [142]. Moreover, supplementation with BA for 4� weeks has been shown to increase knee extension torque by up to 6% [143], improve workload and time to fatigue during high intensity cardio [144-148], improve muscle resistance to fatigue during strength training [149], increase lean mass by approximately 1 kg [147] and significantly reduce perceptions of fatigue [150]. Additionally, the combination of BA and CM may increase performance of high intensity endurance exercise [151] and has been shown to increase lean mass and decrease body fat percentage more than CM alone [152]. However, not all studies have shown improvements in performance with BA supplementation [143,153,154]. To clarify these discrepancies, Hobson et al. [155] conducted a meta-analysis of 15 studies on BA supplementation and concluded that BA significantly increased exercise capacity and improved exercise performance on 60-240 s (ES =𠂐.665) and 𾉀 s (ES = 0.368) exercise bouts.

Although BA appears to improve exercise performance, the long-term safety of BA has only been partially explored. Currently, the only known side effect of BA is unpleasant symptoms of parasthesia reported after consumption of large dosages however, this can be minimized through consumption of smaller dosages throughout the day [142]. While BA appears to be relatively safe in the short-term, the long-term safety is unknown. In cats, an addition of 5 percent BA to drinking water for 20 weeks has been shown to deplete taurine and result in damage to the brain however, taurine is an essential amino acid for cats but not for humans and it is unknown if the smaller dosages consumed by humans could result in similar effects [156]. BA may increase exercise performance and increase lean mass in bodybuilders and currently appears to be safe however, studies are needed to determine the long-term safety of BA consumption.

Beta-hydroxy-beta-methylbutyrate (HMB) is a metabolite of the amino acid leucine that has been shown to decrease muscle protein catabolism and increase muscle protein synthesis [157,158]. The safety of HMB supplementation has been widely studied and no adverse effects on liver enzymes, kidney function, cholesterol, white blood cells, hemoglobin, or blood glucose have been observed [159-161]. Furthermore, two meta-analyses on HMB supplementation have concluded that HMB is safe and does not result in any major side effects [159,160]. HMB may actually decrease blood pressure, total and LDL cholesterol, especially in hypercholesterolemic individuals.

HMB is particularly effective in catabolic populations such as the elderly and patients with chronic disease [162]. However, studies on the effectiveness of HMB in trained, non-calorically restricted populations have been mixed. Reasons for discrepancies in the results of HMB supplementation studies in healthy populations may be due to many factors including clustering of data in these meta-analysis to include many studies from similar groups, poorly designed, non-periodized training protocols, small sample sizes, and lack of specificity between training and testing conditions [163]. However, as a whole HMB appears to be effective in a majority of studies with longer-duration, more intense, periodized training protocols and may be beneficial to bodybuilders, particularly during planned over-reaching phases of training [164]. While the authors hypothesize that HMB may be effective in periods of increased catabolism, such as during contest preparation, the efficacy of HMB on maintenance of lean mass in dieting athletes has not been investigated in a long-term study. Therefore, future studies are needed to determine the effectiveness of HMB during caloric restriction in healthy, lean, trained athletes.

Branched chain amino acids

Branched chain amino acids (BCAA’s) make up 14-18% of amino acids in skeletal muscle proteins and are quite possibly the most widely used supplements among natural bodybuilders [165]. Of the BCAA’s, leucine is of particular interest because it has been shown to stimulate protein synthesis to an equal extent as a mixture of all amino acids [166]. However, ingestion of leucine alone can lead to depletion of plasma valine and isoleucine therefore, all three amino acids need to be consumed to prevent plasma depletion of any one of the BCAA’s [167]. Recently, the safe upper limit of leucine was set at 550 mg/kg bodyweight/day in adult men however, future studies are needed to determine the safe upper limit for both other populations and a mixture of all 3 BCAA’s [168].

Numerous acute studies in animals and humans have shown that consumption of either essential amino acids, BCAA’s, or leucine either at rest or following exercise increases skeletal muscle protein synthesis, decreases muscle protein degradation, or both [27,169-172] however, there are few long-term studies of BCAA supplementation in resistance-trained athletes. Stoppani et al. [173] supplemented trained subjects with either 14 g BCAAs, whey protein, or a carbohydrate placebo for eight weeks during a periodized strength training routine. After training the BCAA group had a 4 kg increase in lean mass, 2% decrease in body fat percentage, and 6 kg increase in bench press 10 repetition maximum. All changes were significant compared to the other groups. However, it should be noted that this data is only available as an abstract and has yet to undergo the rigors of peer-review.

The use of BCAA’s between meals may also be beneficial to keep protein synthesis elevated. Recent data from animal models suggest that consumption of BCAA’s between meals can overcome the refractory response in protein synthesis that occurs when plasma amino acids are elevated, yet protein synthesis is reduced [174]. However, long-term human studies examining the effects of a diet in which BCAA’s are consumed between meals on lean mass and strength have not been done to date. It should also be noted that BCAA metabolism in humans and rodents differ and the results from rodent studies with BCAA’s may not translate in human models [175]. Therefore, long-term studies are needed in humans to determine the effectiveness of this practice.

Based on the current evidence, it is clear BCAA’s stimulate protein synthesis acutely and one study [173] has indicated that BCAA’s may be able to increase lean mass and strength when added to a strength training routine however, additional long-term studies are needed to determine the effects of BCAA’s on lean mass and strength in trained athletes. In addition, studies are needed on the effectiveness of BCAA supplementation in individuals following a vegetarian diet in which consumption of high-quality proteins are low as this may be population that may benefit from BCAA consumption. Furthermore, the effects of BCAA ingestion between meals needs to be further investigated in a long-term human study.

Arginine

“NO supplements” containing arginine are consumed by bodybuilders pre-workout in an attempt to increase blood flow to the muscle during exercise, increase protein synthesis, and improve exercise performance. However, there is little scientific evidence to back these claims. Fahs et al. [176] supplemented healthy young men with 7 g arginine or a placebo prior to exercise and observed no significant change in blood flow following exercise. Additionally, Tang et al. [177] supplemented either 10 g arginine or a placebo prior to exercise and found no significant increase in blood flow or protein synthesis following exercise. Moreover, arginine is a non essential amino acid and prior work has established that essential amino acids alone stimulate protein synthesis [178]. Based on these findings, it appears that arginine does not significantly increase blood flow or enhance protein synthesis following exercise.

The effects of arginine supplementation on performance are controversial. Approximately one-half of acute and chronic studies on arginine and exercise performance have found significant benefits with arginine supplementation, while the other one-half has found no significant benefits [179]. Moreover, Greer et al. [180] found that arginine supplementation significantly reduced muscular endurance by 2𠄴 repetitions on chin up and push up endurance tests. Based on these results, the authors of a recent review concluded that arginine supplementation had little impact on exercise performance in healthy individuals [181]. Although the effects of arginine on blood flow, protein synthesis, and exercise performance require further investigation, dosages commonly consumed by athletes are well below the observed safe level of 20 g/d and do not appear to be harmful [182].

Citrulline malate

Citrulline malate (CitM) has recently become a popular supplement among bodybuilders however, there has been little scientific research in healthy humans with this compound. CitM is hypothesized to improve performance through three mechanisms: 1) citrulline is important part of the urea cycle and may participate in ammonia clearance, 2) malate is a tricarboxylic acid cycle intermediate that may reduce lactic acid accumulation, and 3) citrulline can be converted to arginine however, as discussed previously, arginine does not appear to have an ergogenic effect in young healthy athletes so it is unlikely CitM exerts an ergogenic effect through this mechanism [179,183].

Supplementation with CitM for 15ꃚys has been shown to increase ATP production by 34% during exercise, increase the rate of phosphocreatine recovery after exercise by 20%, and reduce perceptions of fatigue [184]. Moreover, ingestion of 8 g CitM prior to a chest workout significantly increased repetitions performed by approximately 53% and decreased soreness by 40% at 24 and 48 hours post-workout [183]. Furthermore, Stoppani et al. [173] in an abstract reported a 4 kg increase in lean mass, 2 kg decrease in body fat percentage, and a 6 kg increase in 10 repetition maximum bench press after consumption of a drink containing 14 g BCAA, glutamine, and CitM during workouts for eight weeks although, it is not clear to what degree CitM contributed to the outcomes observed. However, not all studies have supported ergogenic effects of CitM. Sureda et al. [185] found no significant difference in race time when either 6 g CitM or a placebo were consumed prior to a 137 km cycling stage. Hickner et al. [186] found that treadmill time to exhaustion was significantly impaired, with the time taken to reach exhaustion occurring on average seven seconds earlier following CitM consumption.

Additionally, the long-term safety of CitM is unknown. Therefore, based on the current literature a decision on the efficacy of CitM cannot be made. Future studies are needed to conclusively determine if CitM is ergogenic and to determine its long term safety.

Glutamine

Glutamine is the most abundant non-essential amino acid in muscle and is commonly consumed as a nutritional supplement. Glutamine supplementation in quantities below 14 g/d appear to be safe in healthy adults [182] however, at present there is little scientific evidence to support the use of glutamine in healthy athletes [187]. Acutely, glutamine supplementation has not been shown to significantly improve exercise performance [188,189], improve buffering capacity [189], help to maintain immune function or reduce muscle soreness after exercise [187]. Long-term supplementation studies including glutamine in cocktails along with CM, whey protein, BCAA’s, and/or CitM have shown 1.5 – 2 kg increases in lean mass and 6 kg increase in 10RM bench press strength [173,190]. However, the role of glutamine in these changes is unclear. Only one study [191] has investigated the effects of glutamine supplementation alone in conjunction with a six week strength training program. No significant differences in muscle size, strength, or muscle protein degradation were observed between groups. Although the previous studies do not support the use of glutamine in bodybuilders during contest preparation, it should be noted that glutamine may be beneficial for gastrointestinal health and peptide uptake in stressed populations [192] therefore, it may be beneficial in dieting bodybuilders who represent a stressed population. As a whole, the results of previous studies do not support use of glutamine as an ergogenic supplement however, future studies are needed to determine the role of glutamine on gastrointestinal health and peptide transport in dieting bodybuilders.

Caffeine

Caffeine is perhaps the most common pre-workout stimulant consumed by bodybuilders. Numerous studies support the use of caffeine to improve performance during endurance training [193,194], sprinting [195,196], and strength training [197-199]. However, not all studies support use of caffeine to improve performance in strength training [200,201]. It should be noted that many of the studies that found increases in strength training performance supplemented with larger (5𠄶 mg/kg) dosages of caffeine. However, this dosage of caffeine is at the end of dosages that are considered safe (6 mg/kg/day) [202]. Additionally, it appears that regular consumption of caffeine may result in a reduction of ergogenic effects [203]. Therefore, it appears that 5𠄶 mg/kg caffeine taken prior to exercise is effective in improving exercise performance however, caffeine use may need to be cycled in order for athletes to obtain the maximum ergogenic effect.

Micronutrients

Several previous studies have observed deficiencies in intakes of micronutrients, such as vitamin D, calcium, zinc, magnesium, and iron, in dieting bodybuilders [3,17,18,204,205]. However, it should be noted that these studies were all published nearly 2 decades ago and that micronutrient deficiencies likely occurred due to elimination of foods or food groups and monotony of food selection [3,205]. Therefore, future studies are needed to determine if these deficiencies would present while eating a variety of foods and using the contest preparation approach described herein. Although the current prevalence of micronutrient deficiencies in competitive bodybuilders is unknown, based on the previous literature, a low-dose micronutrient supplement may be beneficial for natural bodybuilders during contest preparation however, future studies are needed to verify this recommendation.

Peak week

In an attempt to enhance muscle size and definition by reducing extracellular water content, many bodybuilders engage in fluid, electrolyte, and carbohydrate manipulation in the final days and hours before competing [2,60,206]. The effect of electrolyte manipulation and dehydration on visual appearance has not been studied, however it may be a dangerous practice [207]. Furthermore, dehydration could plausibly degrade appearance considering that extracellular water is not only present in the subcutaneous layer. A significant amount is located in the vascular system. Thus, the common practice of "pumping up" to increase muscle size and definition by increasing blood flow to the muscle with light, repetitive weight lifting prior to stepping on stage [208] could be compromised by dehydration or electrolyte imbalance. Furthermore, dehydration reduces total body hydration. A large percentage of muscle tissue mass is water and dehydration results in decreases in muscle water content [209] and therefore muscle size, which may negatively impact the appearance of muscularity.

In the final days before competing, bodybuilders commonly practice carbohydrate loading similar to endurance athletes in an attempt to raise muscle-glycogen levels and increase muscle size [4,18,60,208]. In the only direct study of this practice, no significant quantitative change in muscle girth was found to occur [208]. However, an isocaloric diet was used, with only a change in the percentage of carbohydrate contributing to the diet. If total calories had also been increased, greater levels of glycogen might have been stored which could have changed the outcome of this study. Additionally, unlike the subjects in this study bodybuilders prior to carbohydrate loading have reduced glycogen levels from a long calorically restricted diet and it is possible in this state that carbohydrate loading might effect a visual change. Furthermore, bodybuilding performance is measured subjectively, thus analysis of girth alone may not discern subtle visual changes which impact competitive success. Lastly, some bodybuilders alter the amount of carbohydrate loaded based on the visual outcome, increasing the amount if the desired visual change does not occur [60]. Thus, an analysis of a static carbohydrate load may not accurately represent the dynamic nature of actual carbohydrate loading practices.

In fact, in an observational study of competitive bodybuilders in the days before competition who loaded carbohydrates, subjects showed a 4.9% increase in biceps thickness the final day before competition compared to six weeks prior [4]. Although it is unknown if this was caused by increased muscle glycogen, it is unlikely it was due to muscle mass accrual since the final weeks of preparation are often marked by decreases not increases in LBM [6]. Future studies of this practice should include a qualitative analysis of visual changes and analyze the effects of concurrent increases in percentage of carbohydrates as well as total calories.

At this time it is unknown whether dehydration or electrolyte manipulation improves physique appearance. What is known is that these practices are dangerous and have the potential to worsen it. It is unclear if carbohydrate loading has an impact on appearance and if so, how significant the effect is. However, the recommended muscle-sparing practice by some researchers to increase the carbohydrate content of the diet in the final weeks of preparation [6] might achieve any proposed theoretical benefits of carbohydrate loading. If carbohydrate loading is utilized, a trial run before competition once the competitor has reached or nearly reached competition leanness should be attempted to develop an individualized strategy. However, a week spent on a trial run consuming increased carbohydrates and calories may slow fat loss, thus ample time in the diet would be required.

Psychosocial issues

Competitive bodybuilding requires cyclical periods of weight gain and weight loss for competition. In a study by Anderson et al. [207], it was found that 46% of a group of male drug free bodybuilders reported episodes of binge eating after competitions. One third to half reported anxiety, short tempers or anger when preparing for competition and most (81.5%) reported preoccupation with food.

Competitive male bodybuilders exhibit high rates of weight and shape preoccupation, binge eating and bulimia nervosa. However, they exhibit less eating-related and general psychopathology compared to men already diagnosed with bulimia nervosa [210]. Often they are more focused on muscle gain versus fat loss when compared to males with eating disorders [211]. That being said, this may change during preparation for competition when body builders need to reduce body fat levels.

Muscle dysmorphia is higher in male competitive natural bodybuilders than in collegiate football players and non-competitive weight trainers for physique [212]. However, the psychosocial profile of competitive bodybuilders is rather complex. Despite exhibiting greater risk for eating disturbances and a greater psychological investment in their physical appearance, they may have greater levels of physique satisfaction compared to non-competitive weight lifters and athletically active men [213]. Also, male bodybuilders are not a body-image homogenous group when experience is taken into account. Novice bodybuilders show greater levels of dissatisfaction with their muscle size and greater tendencies towards unhealthy and obsessive behavior [214]. Furthermore, the physical effects of semi-starvation in men can approximate the signs and symptoms of eating disorders such as anorexia nervosa and bulimia nervosa [11]. Thus, many of the psychosocial effects and behaviors seen in competitive bodybuilders may be at least partially the result of a prolonged diet and becoming very lean. When these factors are all considered it may indicate that at least in men, competitive bodybuilding drives certain psychosocial behaviors, in addition to those with prior existing behaviors being drawn to the sport.

However this may not be as much the case with female bodybuilders. Walberg [215] when comparing competitive bodybuilders to non-competitive female weight lifters, found that among bodybuilders 42% used to be anorexic, 67% were terrified of becoming fat, and 50% experienced uncontrollable urges to eat. All of these markers were significantly higher in bodybuilders than in non-competitors. Furthermore, it was found that menstrual dysfunction was more common among the bodybuilders. In agreement with this finding, Kleiner et al. [2] reported that 25% of female bodybuilding competitors reported abnormal menstrual cycles.

Competitive bodybuilders are not alone in their risk and disposition towards behaviors that carry health concerns. Elite athletes in aesthetic and weight-class sports as a whole share these risks [216]. In some sports, minimum body fat percentages can be established and minimum hydration levels for weighing in can be set. However, because bodybuilding performance is directly impacted by body fat percentage and not by weight per se, these regulatory changes to the sport are unlikely. Therefore, competitors and trainers should be aware of the potential psychosocial risks involved with competition. Open and frequent communication on these topics should be practiced and competitors and trainers should be aware of the signs and symptoms of unhealthy behaviors. Early therapeutic intervention by specialists with experience in competitive bodybuilding and eating disorders should occur if disordered eating patterns or psychological distress occurs.

Limitations

The primary limitation of this review is the lack of large-scale long-term studies on competitive natural bodybuilders. To circumvent this, long-term studies on skeletal muscle hypertrophy and body fat loss in athletic dieting human populations were preferentially selected. In the absence of such studies, acute studies and/or animal studies were selected.


Watch the video: Οι Επιπτώσεις Της Κλιματικής Αλλαγής Στην Ελληνική Οικονομία (January 2022).