One of the most common means athletes have employed to increase muscle mass is to add extra calories to the diet. Most athletes "bulk up" in this manner by consuming extra food and/or weight gain powders. Studies have consistently shown that simply adding an extra 500 – 1,000 calories per day to your diet will promote weight gain 2036. However, only about 30 – 50% of the weight gained on high calorie diets is muscle while the remaining amount of weight gained is fat. Consequently, increasing muscle mass by ingesting a high calorie can help you build muscle but the accompanying increase in body fat may not be desirable for everyone. Therefore, we typically do not recommend this type of weight gain approach.

In our view, the most effective nutritional supplement available to athletes to increase high intensity exercise capacity and muscle mass during training is creatine. Numerous studies have indicated that creatine supplementation increases body mass and/or muscle mass during training 53 Gains are typically 2 – 5 pounds greater than controls during 4 – 12 weeks of training 54. The gains in muscle mass appear to be a result of an improved ability to perform high intensity exercise enabling an athlete to train harder and thereby promote greater training adaptations and muscle hypertrophy 555657. The only clinically significant side effect reported from creatine supplementation has been weight gain 36535458 Although concerns have been raised about the safety and possible side effects of creatine supplementation 5960, recent long-term safety studies have reported no apparent side effects 586162 and/or that creatine may lessen the incidence of injury during training 636465. Consequently, supplementing the diet with creatine and/or creatine containing formulations seems to be a safe and effective method to increase muscle mass.

HMB is a metabolite of the amino acid leucine. Leucine and metabolites of leucine have been reported to inhibit protein degradation 66. Supplementing the diet with 1.5 to 3 g/d of calcium HMB has been typically reported to increase muscle mass and strength particularly among untrained subjects initiating training 676869707172 and the elderly 73. Gains in muscle mass are typically 0.5 to 1 kg greater than controls during 3 – 6 weeks of training. There is also recent evidence that HMB may lessen the catabolic effects of prolonged exercise 74 and that there may be additive effects of co-ingesting HMB with creatine 7576. However, the effects of HMB supplementation in athletes are less clear. Most studies conducted on trained subjects have reported non-significant gains in muscle mass possibly due to a greater variability in response of HMB supplementation among athletes 777879. Consequently, there is fairly good evidence showing that HMB may enhance training adaptations in individuals initiating training. However, additional research is necessary to determine whether HMB may enhance training adaptations in athletes.

BCAA supplementation has been reported to decrease exercise-induced protein degradation and/or muscle enzyme release (an indicator of muscle damage) possibly by promoting an anti-catabolic hormonal profile 363880. Theoretically, BCAA supplementation during intense training may help minimize protein degradation and thereby lead to greater gains in fat-free mass. There is some evidence to support this hypothesis. For example, Schena and colleagues 81 reported that BCAA supplementation (~10 g/d) during 21-days of trekking at altitude increased fat free mass (1.5%) while subjects ingesting a placebo had no change in muscle mass. Bigard and associates 82 reported that BCAA supplementation appeared to minimize loss of muscle mass in subjects training at altitude for 6-weeks. Finally, Candeloro and coworkers 83 reported that 30 days of BCAA supplementation (14 grams/day) promoted a significant increase in muscle mass (1.3%) and grip strength (+8.1%) in untrained subjects. Although more research is necessary, these findings suggest that BCAA supplementation may have some impact on body composition.

Recent studies have indicated that ingesting 3 to 6 g of EAA prior to 8485 and or following exercise stimulates protein synthesis 8586878889909192. Theoretically, this may enhance gains in muscle mass during training. To support this theory, a recent study by Esmarck and colleagues 93 found that ingesting EAA with carbohydrate immediately following resistance exercise promoted significantly greater training adaptations as compared to waiting until 2-hours after exercise to consume the supplement. Although more data is needed, there appears to be strong theoretical rationale and some supportive evidence that EAA supplementation may enhance protein synthesis and training adaptations.

Glutamine is the most plentiful non-essential amino acid in the body and plays a number of important physiological roles 36. Glutamine has been reported to increase cell volume and stimulate protein 949596 and glycogen synthesis 97. Theoretically, glutamine supplementation prior to and/or following exercise (e.g., 6–10 g) may help to optimize cell hydration and protein synthesis during training leading to greater gains in muscle mass and strength 3698. In support of this hypothesis, a recent study by Colker and associates 99 found that subjects who supplemented their diet with glutamine (5 grams) and BCAA (3 grams) enriched whey protein during training promoted about a 2 pound greater gain in muscle mass and greater gains in strength than ingesting whey protein alone. Although more data is needed, there appears to be a strong scientific rationale and some preliminary evidence to indicate that glutamine may help build muscle.

As previously described, research has indicated that people undergoing intense training may need additional protein in their diet to meet protein needs (i.e., 1.5 – 2.0 grams/day). People who do not ingest enough protein in their diet may slow recovery and training adaptations 36. Protein supplements offer a convenient way to ensure that athletes consume quality protein in the diet and meet their protein needs. However, ingesting additional protein beyond that necessary to meet protein needs does not appear to promote additional gains in strength and muscle mass. The research focus over recent years has been to determine whether different types of protein (e.g., whey, casein, soy, milk proteins, colostrum, etc) and/or various biologically active protein subtypes and peptides (e.g., α-lactalbumin, β-lactoglobulin, glycomacropeptides, immunoglobulins, lactoperoxidases, lactoferrin, etc) have varying effects on the physiological, hormonal, and/or immunological responses to training. In addition, whether timing of protein intake may play a role in protein synthesis and training adaptations 8586878889909192. Although more research is necessary in this area, research clearly indicates that protein needs of individuals engaged in intense training are elevated, that different types of protein have varying effects on anabolism and catabolism, that different types of protein subtypes and peptides have unique physiological effects, and that timing of protein intake may play an important role in optimizing protein synthesis following exercise. Therefore, it is simplistic and misleading to suggest that there is no data supporting contentions that athletes need more protein in their diet and/or there is no potential ergogenic value of incorporating different types of protein into the diet.

α-KG is an intermediate in the Krebs cycle that is involved in aerobic energy metabolism. There is some clinical evidence that α-KG may serve as an anticatabolic nutrient after surgery 100101. However, it is unclear whether α-KG supplementation during training may affect training adaptations.

KIC is a branched-chain keto acid that is a metabolite of leucine metabolism. In a similar manner as HMB, leucine and metabolites of leucine are believed to possess anticatabolic properties 102. There is some clinical evidence that KIC may spare protein degradation in clinical populations 103104. Theoretically, KIC may help minimize protein degradation during training possibly leading to greater training adaptations. However, we are not aware of any studies that have evaluated the effects of KIC supplementation during training on body composition.

Ecdysterones (also known as ectysterone, 20 Beta-Hydroxyecdysterone, turkesterone, ponasterone, ecdysone, or ecdystene) are naturally derived phytoecdysteroids (i.e., insect hormones). They are typically extracted from the herbs Leuza rhaptonticum sp., Rhaponticum carthamoides, or Cyanotis vaga. They can also be found in high concentrations in the herb Suma (also known as Brazilian Ginseng or Pfaffia). Research from Russia and Czechoslovakia conducted over the last 30 years indicates that ecdysterones may possess some potentially beneficial physiological effects in insects and animals 105106107108109. However, since most of the data on ecdysterones have been published in obscure journals, results are difficult to interpret. While future studies may find some ergogenic value of ecdysterones, it is our view that it is too early to tell whether phytoecdysteroids serve as a safe and effective nutritional supplement for athletes.

Research has indicated that growth hormone releasing peptides (GHRP) and other non-peptide compounds (secretagogues) appear to help regulate growth hormone (GH) release 110111. These observations have served as the basis for development of nutritionally-based GH stimulators (e.g., amino acids, pituitary peptides, "pituitary substances", macuna pruriens, broad bean, alpha GPC, etc). Although there is clinical evidence that pharmaceutical grade GHRP's and some non-peptide secretagogues can increase GH and IGF-1 levels at rest and in response to exercise, it is currently unknown whether any of these nutritional alternatives would increase GH and/or affect training adaptations.

Isoflavones are naturally occurring non-steroidal phytoestrogens that have a similar chemical structure as the ipriflavone (a synthetic flavonoid drug used in the treatment of osteoporosis) 112113114. For this reason, soy protein (which is an excellent source of isoflavones) and isoflavone extracts have been investigated in the possible treatment of osteoporosis. Results of these studies have shown promise in preventing declines in bone mass in post-menopausal women as well as reducing risks to side effects associated with estrogen replacement therapy. More recently, the isoflavone extracts 7-isopropoxyisoflavone (ipriflavone) and 5-methyl-7-methoxy-isoflavone (methoxyisoflavone) have been marketed as "powerful anabolic" substances. These claims have been based on research described in patents filed in Hungary in the early 1970s 115116. Although the data presented in the patents are interesting, there is currently no peer-reviewed data indicating that isoflavone supplementation affects exercise, body composition, or training adaptations.

OKG is another nutrient believed to possess anabolic/catabolic effect. Animal and clinical studies have suggested that patients administered OKG experienced improved protein balance 115116. Theoretically, OKG may provide some value for athletes engaged in intense training. A recent study by Chetlin and colleagues 117 reported that OKG supplementation (10 grams/day) during 6-weeks of resistance training promoted greater gains in bench press. However, no significant differences were observed in squat strength, training volume, gains in muscle mass, or fasting insulin and growth hormone. Therefore, additional research is needed before conclusions can be drawn.

Myostatin or growth differentiation factor 8 (GDF-8) is a transforming growth factor that has been shown to serve as a genetic determinant of the upper limit of muscle size and growth 118. Recent research has indicated that eliminating and/or inhibiting myostatin gene expression in mice 119 and cattle 120121122 promotes marked increases in muscle mass during early growth and development. The result is that these animals experience what has been termed as a "double-muscle" phenomenon apparently by allowing muscle to grow beyond its normal genetic limit. In agriculture research, eliminating and/or inhibiting myostatin may serve as an effective way to optimize animal growth leading to larger, leaner, and a more profitable livestock yield. In humans, inhibiting myostatin gene expression has been theorized as a way to prevent or slow down muscle wasting in various diseases, speed up recovery of injured muscles, and/or promote increases in muscle mass and strength in athletes 123. While these theoretical possibilities may have great promise, research on the role of myostatin inhibition on muscle growth and repair is in the very early stages – particularly in humans. There is some evidence that myostatin levels are higher in the blood of HIV positive patients who have experience muscle wasting and that myostatin levels negatively correlate with muscle mass 118. There is also evidence that myostatin gene expression may be fiber specific and that myostatin levels may be influenced by immobilization in animals 124. Additionally, a recent study by Ivey and colleagues 123 reported that female athletes with a less common myostatin allele (a genetic subtype that may be more resistant to myostatin) experienced greater gains in muscle mass during training and less loss of muscle mass during detraining. No such pattern was observed in men with varying amounts of training histories and muscle mass. These early studies suggest that myostatin may play a role in regulating muscle growth to some degree. Recently, some nutrition supplement companies have marketed sulfo-polysaccharides (derived from a sea algae called Cytoseira canariensis) as a way to partially bind the myostatin protein in serum. Although this theory is interesting and studies examining this hypothesis are underway, there is currently no published data supporting the use of sulfo-polysaccharides as a muscle building supplement.

SO is a compound which contains plant sterols purported to enhance immunity as well as provide an androgenic effect on muscle growth 1. Some data supports the potential immune enhancing effects of SO. However, we are not aware of any data that show that SO supplementation increases muscle mass during training.

ZMA formulations have recently become a popular supplement purported to promote anabolism at night. The theory is based on studies suggesting that zinc and magnesium deficiency may reduce the production of testosterone and insulin like growth factor (IGF-1). ZMA supplementation has been theorized to increase testosterone and IGF-1 leading to greater recovery, anabolism, and strength during training. In support of this theory, Brilla and Conte 125 reported that a zinc-magnesium formulation increased testosterone and IGF-1 (two anabolic hormones) leading to greater gains in strength in football players participating in spring training. While these data are interesting, more research is needed to further evaluate the role of ZMA on body composition and strength during training before conclusions can be drawn.

Boron is a trace mineral proposed to increase testosterone levels and promote anabolism. Several studies have evaluated the effects of boron supplementation during training on strength and body composition alterations. These studies indicate that boron supplement (2.5 mg/d) appears to have no impact on muscle mass or strength 126127.

Chromium is a trace mineral that is involved in carbohydrate and fat metabolism. Clinical studies have suggested that chromium may enhance the effects of insulin particularly in diabetic populations. Since insulin is an anti-catabolic hormone and has been reported to affect protein synthesis, chromium supplementation has been theorized to serve as an anabolic nutrient. Theoretically, this may increase anabolic responses to exercise. Although some initial studies reported that chromium supplementation increased gains in muscle mass and strength during training particularly in women 128129130, most well-controlled that have been conducted since then have reported no benefit in healthy individuals taking chromium (200–800 mcg/d) for 4 to 16-weeks during training 131132133134135136137. Consequently, it appears that although chromium supplementation may have some therapeutic benefits for diabetics, chromium does not appear to be a muscle-building nutrient for athletes.

Animal studies indicate that adding CLA to dietary feed decreases body fat, increases muscle and bone mass, has anti-cancer properties, enhances immunity, and inhibits progression of heart disease 138139140. Consequently, CLA supplementation in humans has been suggested to help manage body composition, delay loss of bone, and provide health benefit. Although animal studies are impressive 141142143 and a some studies suggests benefit at some but not all dosages 144145, most studies conducted on humans show little to no effect on body composition or muscle growth 146147

Gamma oryzanol is a plant sterol theorized to increase anabolic hormonal responses during training 148. Although data are limited, one study reported no effect of 0.5 g/d of gamma oryzanol supplementation on strength, muscle mass, or anabolic hormonal profiles during 9-weeks of training 149.

Testosterone and growth hormone are two primary hormones in the body that serve to promote gains in muscle mass (i.e., anabolism) and strength while decreasing muscle breakdown (catabolism) and fat mass 150151152153154. Testosterone also promotes male sex characteristics (e.g., hair, deep voice, etc) 154. Low level anabolic steroids are often prescribed by physicians to prevent loss of muscle mass for people with various diseases and illnesses 155156157158159160161162163164165166. It is well known that athletes have experimented with large doses of anabolic steroids in an attempt to enhance training adaptations, increase muscle mass, and/or promote recovery during intense training 150151152153154. Research has generally shown that use of anabolic steroids and growth hormone during training can promote gains in strength and muscle mass 150160167168169170171172173174. However, a number of potentially life threatening adverse effects of steroid abuse have been reported including liver and hormonal dysfunction, hyperlipidemia (high cholesterol), increased risk to cardiovascular disease, and behavioral changes (i.e., steroid rage) 169175176177178179. Some of the adverse effects associated with the use of these agents are irreversible, particularly in women 176. For this reason, anabolic steroids have has been banned by most sport organizations and should be avoided unless prescribed by a physician to treat an illness.

Prohormones (androstenedione, 4-androstenediol, 19-nor-4-androstenedione, 19-nor-4-androstenediol, 7-keto DHEA, and DHEA, etc) are naturally derived precursors to testosterone or other anabolic steroids. Prohormones have become popular among body builders because they believe they are natural boosters of anabolic hormones. Consequently, a number of over-the-counter supplements contain prohormones. While there is a strong theoretical rationale that prohormones may increase testosterone levels, there is virtually no evidence that these compounds affect training adaptations in younger men with normal hormone levels. In fact, most studies indicate that they do not affect testosterone and that some may actually increase estrogen levels and reduce HDL-cholesterol 169180181182183184185186. Consequently, although there may be some potential applications for older individuals to replace diminishing androgen levels, it appears that prohormones have no training value. Since prohormones are "steroid-like compounds", most athletic organizations have banned their use. Use of nutritional supplements containing prohormones will result in a positive drug test for anabolic steroids. Use of supplements knowingly or unknowingly containing prohormones have been believed to have contributed to a number of recent positive drug tests among athletes. Consequently, care should be taken to make sure that any supplement an athlete considers taking does not contain prohormone precursors particularly if their sport bans and tests for use of such compounds.

Tribulus terrestris (also known as puncture weed/vine or caltrops) is a plant extract that has been suggested to stimulate leutinizing hormone (LH) which stimulates the natural production of testosterone 102. Consequently, Tribulus has been marketed as a supplement that can increase testosterone and promote greater gains in strength and muscle mass during training. Several recent studies have indicated that Tribulus supplementation appears to have no effects on body composition or strength during training 187188.

In a similar manner as chromium, vanadyl sulfate is a trace mineral that has been found to affect insulin-sensitivity and may affect protein and glucose metabolism 102. For this reason, vanadyl sulfate has been purported to increase muscle mass and strength during training. Although there may be some clinical benefits for diabetics, vanadyl sulfate supplementation does not appear to have any effect on strength or muscle mass during training in non-diabetic individuals 189190.

Although exercise and proper diet remain the best way to promote weight loss and/or manage body composition, a number of nutritional approaches have been investigated as possible weight loss methods (with or without exercise). The following overviews the major types of weight loss products available and discusses whether any available research supports their use. See Table 3 for a summary.

Most of the products in this category represent low fat/carbohydrate, high protein food alternatives 191. They typically consist of pre-packaged food, bars, MRP, or RTD supplements. They are designed to provide convenient foods/snacks to help people follow a particular low calorie diet plan. In the scientific literature, diets that provide less than 1000 calories per day are known as very low calorie diets (VLCD's). Pre-packaged food, MRP's, and/or RTD's are often provided in VLCD plans to help people cut calories. In most cases, VLCD plans recommend behavioral modification and that people start a general exercise program.

Research on the safety and efficacy of people maintaining VLCD's generally indicate that they can promote weight loss. For example, Hoie et al 192 reported that maintaining a VLCD for 8-weeks promoted a 27 lbs (12.6%) loss in total body mass, a 21 lbs loss in body fat (23.8%), and a 7 lbs (5.2%) loss in lean body mass in 127 overweight volunteers. Bryner and colleagues 193 reported that addition of a resistance training program while maintaining a VLCD (800 kcal/d for 12-weeks) resulted in a better preservation of lean body mass and resting metabolic rate compared to subjects maintaining a VLCD while engaged in an endurance training program. Kern and coworkers 194 reported that a medically supervised weight loss program involving behavioral modification and VLCD promoted a 51 lbs weight loss and that 61% of subjects maintained at least 50% of the weight loss at 12 and 18 months follow-up. Recent studies indicate that high protein/low fat VLCD's may be better than high carbohydrate/low fat diets in promoting weight loss 32195196197198. The reason for this is that typically when people lose weight about 40–50% of the weight loss is muscle which decreases resting energy expenditure. Increasing protein intake during weight loss helps preserve muscle mass and resting energy expenditure to a better degree than high carbohydrate diets 199. These findings and others indicate that VLCD's (typically using MRP's and/or RTD's as a means to control caloric intake) can be effective particularly as part of an exercise and behavioral modification program. Most people appear to maintain at least half of the initial weight lost for 1–2 years but tend to regain most of the weight back within 2–5 years. Therefore, although these diets may help people lose weight on the short-term, it is essential people who use them follow good diet and exercise practices in order to maintain the weight loss.

Thermogenics are supplements designed to stimulate metabolism thereby increasing energy expenditure and promote weight loss. They typically contain the "ECA" stack of ephedra alkaloids (e.g., Ma Haung, 1R,2S Nor-ephedrine HCl, Sida Cordifolia), caffeine (e.g., Gaurana, Bissey Nut, Kola) and aspirin/salicin (e.g., Willow Bark Extract). More recently, other potentially thermogenic nutrients have been added to various thermogenic formulations. For example, thermogenic supplements may also contain synephrine (e.g., Citrus Aurantum, Bitter Orange), calcium & sodium phosphate, thyroid stimulators (e.g., guggulsterones, L-tyrosine, iodine), cayenne & black pepper, and ginger root.

A significant amount of research has evaluated the safety and efficacy of EC and ECA type supplements. Studies show that use of synthetic or herbal sources of ephedrine and caffeine (EC) promote about 2 lbs of extra weight loss per month while dieting (with or without exercise) and that EC supplementation is generally well tolerated in healthy individuals 200201202203204205206207208209. For example, Boozer et al 201 reported that 8-weeks of ephedrine (72 mg/d) and caffeine (240 mg/d) supplementation promoted a 9 lbs loss in body mass and a 2.1% loss in body fat with minor side effects. Molnar and associates 200 reported that overweight children treated for 20 weeks with ephedrine and caffeine observed a 14.4% loss in body mass and a 6.6% decrease in body fat with no differences in side effects. Interestingly, Greenway and colleagues 208 reported that EC supplementation was a more cost-effective treatment for reducing weight, cardiac risk, and LDL cholesterol than several weight loss drugs (fenfluramine with mazindol or phentermine). Finally, Boozer and associates 200 reported that 6-months of herbal EC supplementation promoted weight loss with no clinically significant adverse effects in healthy overweight adults. Less is known about the safety and efficacy of synephrine, thyroid stimulators, cayenne/black pepper and ginger root.

Despite these findings, the Food and Drug Administration (FDA) has recently banned the sale of ephedra containing supplements. The rationale has been based on reports to adverse event monitoring systems and in the media suggesting a link between intake of ephedra and a number of severe medical complications (e.g., high blood pressure, elevated heart rate, arrhythmias, sudden death, heat stroke, etc) 210211. Although results of available clinical studies do not show these types of adverse events and the ban is in the process of being contested legally, ephedra is no longer available as an ingredient in dietary supplements. Consequently, thermogenic supplements now contain other nutrients believed to increase energy expenditure (e.g., synephrine, green tea, etc). Anyone contemplating taking thermogenic supplements should carefully consider the potential side effects, discuss possible use with a knowledgeable physician, and be careful not exceed recommended dosages.

One oldest and most common methods of suppressing the appetite is to eat a high fiber diet. Ingesting high fiber foods (fruits, vegetables) or fiber supplements increase the feeling of fullness (satiety). They typically allow you to feel full while ingesting fewer calories. Theoretically, maintaining a high fiber diet may serve to help decrease the amount of food you eat. In addition, high fiber diets/supplements have also been purported to help lower cholesterol and blood pressure as well as help diabetics manage glucose and insulin levels. Some of the research conducted on high fiber diets indicates that they provide some benefit, particularly in diabetic populations. For example, Raben et al 212 reported that subjects maintaining a low fat/high fiber diet for 11 weeks lost about 3 lbs of weight and 3.5 lbs of fat. Other studies report either no significant effects or modest amounts of fat loss. High fiber/low fat diets have also been found to help reduce cholesterol. Consequently, although maintaining a low fat/high fiber diet may have some health benefits, they do not appear to promote a significant amount of weight or fat loss.

Research has indicated that calcium modulates 1,25-diydroxyvitamin D which serves to regulate intracellular calcium levels in fat cells 213214215. Increasing dietary availability of calcium reduces 1,25-diydroxyvitamin D and promotes reductions in fat mass in animals 213214215. Dietary calcium has been shown to suppress fat metabolism and weight gain during periods of high caloric intake 213216. Further, increasing calcium intake has been shown to increase fat metabolism and preserve thermogenesis during caloric restriction 213216217. In support of this theory, Davies and colleagues 218 reported that dietary calcium was negatively correlated to weight and that calcium supplementation (1,000 mg/d) accounted for an 8 kg weight loss over a 4 yr period. Additionally, Zemel and associates 213 reported that supplemental calcium (800 mg/d) or high dietary intake of calcium (1,200 – 1,300 mg/d) during a 24-week weight loss program promoted significantly greater weight loss (26–70%) and dual energy x-ray absorptiometer (DEXA) determined fat mass loss (38–64%) compared to subjects on a low calcium diet (400–500 mg/d). These findings and others suggest a strong relationship between calcium intake and fat loss.

The role of sodium and calcium phosphate on energy metabolism and exercise performance has been studied for decades 36. These studies have revealed that sodium phosphate supplementation appears to possess ergogenic properties particularly in endurance exercise events 219220. More recently, phosphate supplementation has also been suggested to affect energy expenditure. For example, Kaciuba-Uscilko and colleagues 221 reported that phosphate supplementation during a 4-week weight loss program increased resting metabolic rate (RMR) and respiratory exchange ratio (suggesting greater carbohydrate utilization and caloric expenditure) during submaximal cycling exercise. In addition, Nazar and coworkers 222 reported that phosphate supplementation during an 8-week weight loss program increased RMR by 12–19% and prevented a normal decline in thyroid hormones. Although the rate of weight loss was similar in this trial, results suggest that phosphate supplementation may influence metabolic rate possibly by affecting thyroid hormones. Consequently, it is possible that phosphate could serve as a potential thermogenic nutrient in non-ephedrine based supplements. Additional research is necessary to test this hypothesis.

Green tea is one of the more interesting herbal supplements that has recently been suggested to affect weight loss. Green tea contains high amounts of caffeine and catechin polyphenols. Research suggests that catechin polyphenols possess antioxidant properties 223. In addition, green tea has also been theorized to increase energy expenditure by stimulating brown adipose tissue thermogenesis. In support of this theory, Dulloo et al 224225 reported that green tea supplementation in combination with caffeine (e.g., 50 mg caffeine and 90 mg epigallocatechin gallate taken 3-times per day) significantly increased 24-hour energy expenditure and fat utilization in humans. The thermogenic effects of green tea supplementation were much greater than when an equivalent amount of caffeine was evaluated suggesting a synergistic effect. Theoretically, increases in energy expenditure may help individuals lose weight and/or manage body composition.

Calcium Pyruvate is supplement that hit the scene about five or six years ago with great promise. The theoretical rationale was based on studies from the early 1990s that reported that calcium pyruvate supplementation (16 – 25 g/d with or without dihydroxyacetone phosphate [DHAP]) promoted fat loss in overweight/obese patients following a medially supervised weight loss program 226227228. Although the mechanism for these findings was unclear, the researchers speculated that it might be related to appetite suppression and/or altered carbohydrate and fat metabolism. Since calcium pyruvate is very expensive, several studies have attempted to determine whether ingesting smaller amounts of calcium pyruvate (6–10 g/d) affect body composition in untrained and trained populations. Results of these studies are mixed. Kalman and colleagues 229 reported that calcium pyruvate supplementation (6 g/d for 6-weeks) significantly decreased body weight (-1.2 kg), body fat (-2.5 kg), and percent body fat (-2.7%). However, Stone and colleagues 230 reported that pyruvate supplementation did not affect hydrostatically determined body composition during 5-weeks of in-season college football training. These findings indicate that although there is some supportive data indicating that calcium pyruvate supplementation may enhance fat loss when taken at high doses (6–16 g/d), there is no evidence that ingesting the doses typically found in pyruvate supplements (0.5 – 2 g/d) has any affect on body composition.

Gymnema Sylvestre is a relatively new supplement. It is purported to affect glucose and fat metabolism as well as inhibit sweet cravings. In support of these contentions, some recent data have been published by Shigematsu and colleagues 231232 indicating that short and long-term oral supplementation of gymnema sylvestre in rats fed normal and high-fat diets may have some positive effects on fat metabolism, blood lipid levels, and/or weight gain/fat deposition. Although these findings are interesting, we are aware of no published studies that have evaluated the effects of gymnema sylvestre supplementation on lipid metabolism or body composition in humans. Consequently, more research is needed before conclusions can be drawn.

Chitosan has been marketed as a weight loss supplement for several years. It is purported to inhibit fat absorption and lower cholesterol. Several animal studies report decreased fat absorption, increased fecal fat content, and/or lower cholesterol following chitosan feedings 233234235236 However, the effects in humans appear to be less impressive. For example, although there is some data suggesting that chitosan supplementation may lower blood lipids in humans, 237 other studies report no effects on fecal fat content 238 or body composition alterations 239240 when administered to people following their normal diet. It seems that people may be prone to eat more when they know they are taking a fat blocking supplement in a similar way people tend to eat more when the consume low-fat foods. Whether chitosan may promote greater amounts of fat loss when people are put on a controlled diet is unclear.

Since the safety of ephedra supplements has come into question, a number of supplement companies have been looking for alternatives to ephedra such as Citrus Aurantum or Bitter Orange (synephrine), thyroid stimulators, and various herbs and peppers (cayenne, black pepper, ginger root, etc) 191. Of these, Citrus Aurantum (synephrine) appears to have the most promise 241242. Some studies suggest that synephrine may increase metabolism without significantly affecting heart rate and blood pressure. However, it is unclear whether dietary supplementation of Citrus Aurantum may enhance weight loss. A number of thyroid stimulating supplements have also been marketed. Most contain nutrients (e.g., guggulsterones, 3, 5-Diiodo-L-Thyronine, etc.) believed to enhance the conversion of triidiothyronine (T3) to thyroxin (T4) or increase availability of T2 (diidiothyronine) or T3 which would theoretically increase basal metabolic rate (resting caloric expenditure) and promote weight loss 243244. However, while thyroid medications can effectively increase metabolic rate 245, it is unclear whether these supplements can promote weight loss. Additionally, several of these types of supplements have been recently pulled by the FDA due to adverse health outcomes reported among people using these types of supplements particularly if they also contain usnic acid.

Choline is considered an essential nutrient that is needed for cell membrane integrity and to facilitate the movement of fats in and out of cells. It is also a component of the neurotransmitter acetylcholine and is needed for normal brain functioning, particularly in infants. For this reason, phosphatidyl choline (PC) has been purported as a potentially effective supplement to promote fat loss as well as improve neuromuscular function. There is some data from animal studies that supports the potential value of PC as a weight loss supplement 246. There has also been some interest in determining the potential ergogenic value of choline supplementation during endurance exercise 247248. However, it is currently unclear whether PC supplementation affects body composition in humans.

Betaine is a compound that is involved in the metabolism of choline and homocysteine. A number of studies have evaluated the effects of betaine feedings on liver metabolism, fat metabolism, and fat deposition in animals 249250. There has also been interest in determining whether betaine supplementation may help lower homocysteine levels which has recently been identified as a marker of risk to heart disease 251. For this reason, betaine supplements have been marketed as a supplement designed to promote heart health as well as a weight loss. Although the potential theoretical rationale of betaine supplementation is interesting, it is currently unclear whether betaine supplementation may serve as an effective weight loss supplement in humans.

Forskolin is another relatively new weight loss supplement. Forskolin is a plant native to India that has been used for centuries in traditional Ayurvedic medicine primarily to treat skin disorders and respiratory problems 252253. A considerable amount of research has evaluated the physiological and potential medical applications of forskolin over the last 25 years. Forskolin has been reported to reduce blood pressure, increase the hearts ability to contract, help inhibit platelet aggregation, improve lung function, and aid in the treatment of glaucoma 252253254. With regard to weight loss, forskolin has been reported to increase cyclic AMP and thereby stimulate fat metabolism 255256257. Theoretically, forskolin may therefore serve as an effective weight loss supplement. In support of this theory, Sabinsa Corporation (the principle source for Forskolin in the U.S.) reported that forskolin supplementation (250 mg of a 10% forskolin extract taken twice daily for 8-weeks) administered in an open label manner to six overweight females promoted a 7.25 lbs loss in body weight and a 7.7% decrease bioelectrical impedance (BIA) determined body fat 258. Although this was not a placebo controlled double blind study and BIA is not the most accurate method of assessing body composition, these preliminary findings provide some support to contentions that forskolin supplementation may promote fat loss. Another recent study suggested that supplementing the diet with coleus forskohlii in overweight women helped maintain weight and was not associated with any clinically significant adverse events 259. Additional research is needed before conclusions can be drawn.

Dehydroepiandrosterone (DHEA) and its sulfated conjugate DHEAS represent the most abundant adrenal steroids in circulation 260. Although, DHEA is considered a weak androgen, it can be converted to the more potent androgens testosterone and dihydrotestosterone in tissues. In addition, DHEAS can be converted into androstenedione and testosterone. DHEA levels have been reported to decline with age in humans 261. The decline in DHEA levels with aging has been associated with increased fat accumulation and risk to heart disease 262. Since DHEA is a naturally occurring compound, it has been suggested that dietary supplementation of DHEA may help maintain DHEA availability, maintain and/or increase testosterone levels, reduce body fat accumulation, and/or reduce risk to heart disease as one ages 260262. Although animal studies have generally supported this theory, the effects of DHEA supplementation on body composition in human trials have been mixed. For example, Nestler and coworkers 263 reported that DHEA supplementation (1,600 mg/d for 28-d) in untrained healthy males promoted a 31% reduction in percentage of body fat. However, Vogiatzi and associates 264 reported that DHEA supplementation (40 mg/d for 8 wks) had no effect on body weight, percent body fat, or serum lipid levels in obese adolescents. More recently, 7-keto DHEA has been marketed as a potentially more effective form of DHEA. 7-keto DHEA is a precursor to DHEA that is believed to possess lypolytic properties. Although data are limited, Kalman and colleagues and coworkers 265 reported that 7-keto DHEA supplementation (200 mg/d) during 8-weeks of training promoted a greater loss in body mass and fat mass while increasing T3. No significant effects were observed on thyroid stimulating hormone (TSH), T4, or other hormones. Although more research is needed, these findings provide some support to contentions that 7-keto DHEA may serve as an effective weight loss supplement. However, additional research is needed before definitive conclusions can be made.

This is a relatively new type of weight loss supplement category. Psychotropic nutrients/herbs often contain things like St. John's Wart, Kava, Ginkgo Biloba, Ginseng, and L-Tyrosine. They are believed to serve as naturally occurring antidepressants, relaxants, and mental stimulants. The theoretical rationale regarding weight loss is that they may help people fight depression or maintain mental alertness while dieting. Although a number of studies support potential role as naturally occurring psychotropics or stimulants, the potential value in promoting weight loss is unclear.

Interest in chromium as a potential body composition modifier emanated from studies suggesting that chromium may enhance insulin sensitivity/glucose disposal in diabetics. Initial studies reported that chromium supplementation during resistance training improved fat loss and gains in lean body mass 128129130. However, recent studies using more accurate methods of assessing body composition have mostly reported no effects on body composition in healthy non-diabetic individuals 131132133134135136137. For example, Walker and colleagues 132 reported that chromium supplementation (200 μg/d for 14-weeks) did not affect body composition alterations during training in healthy wrestlers. Likewise, Lukaski et al 136 reported that 8-weeks of chromium supplementation during resistance training did not affect strength or DEXA determined body composition changes. Therefore, chromium supplementation does not appear to promote fat loss.

CLA is a term used to describe a group of positional and geometric isomers of linoleic acid that contain conjugated double bonds. Adding CLA to the diet has been reported to possess significant health benefits in animals 138266. In terms of weight loss, CLA feedings to animals have been reported to markedly decrease body fat accumulation 138139143. Consequently, CLA has been marketed as a health and weight loss supplement since the mid 1990s. Although basic research in animals is very promising, the effect of CLA supplementation in humans is less clear. There are some data suggesting that CLA supplementation may modestly promote fat loss and/or increases in lean mass 144267271. However, other studies indicate that CLA supplementation (1.7 to 12 g/d for 4-weeks to 6-months) has limited to no effects on body composition alterations in untrained or trained populations 144146147267272273274. The reason for the discrepancy in research findings has been suggested to be due to differences in purity and the specific isomer studied. For instance, early studies in humans showing no effect used CLA that contained all 24 isomers. Today, most labs studying CLA use 50–50 mixtures containing the trans-10,cis-12 and cis-9,trans-11 isomers, the former of which being recently implicated in positively altering body composition. In our view, although CLA supplementation may have promise to promote general health, additional research is needed to determine if specific isomers of CLA may affects body composition in humans before conclusions can be made.

HCA is a nutrient that has been hypothesized to increase fat oxidation by inhibiting citrate lyase and lipogenesis 275. Theoretically, this may lead to greater fat burning and weight loss over time. Although there is some evidence that HCA may increase fat metabolism in animal studies, there is little to no evidence showing that HCA supplementation affects body composition in humans. For example, Ishihara et al 276 reported that HCA supplementation spared carbohydrate utilization and promoted lipid oxidation during exercise in mice. However, Kriketos and associates 277 reported that HCA supplementation (3 g/d for 3-days) did not affect resting or post-exercise energy expenditure or markers of lipolysis in healthy men. Likewise, Heymsfield and coworkers 278 reported that HCA supplementation (1.5 g/d for 12-weeks) while maintaining a low fat/high fiber diet did not promote greater weight or fat loss than subjects on placebo. Finally, Mattes and colleagues 279 reported that HCA supplementation (2.4 g/d for 12-weeks) did not affect appetite, energy intake, or weight loss. These findings suggest that HCA supplementation does not appear to promote fat loss in humans.

Carnitine serves as an important transporter of fatty acids from the cytosol into the mitochondria of the cell. Theoretically, increasing cellular levels of carnitine would thereby enhance transport of fats into the mitochondria and fat metabolism. For this reason, L-carnitine has been one of the most common nutrients found in various weight loss supplements. Over the years, a number of studies have been conducted on the effects of L-carnitine supplementation on fat metabolism, exercise capacity and body composition. Although there is some data showing that L-carnitine supplementation may be beneficial for some patient populations, most well controlled studies indicate that L-carnitine supplementation does not affect muscle carnitine content, fat metabolism, and/or weight loss in overweight or trained subjects 280. For example, Villani et al 281 reported that L-carnitine supplementation (2 g/d for 8-weeks) did not affect weight loss, body composition, or markers of fat metabolism in overweight women.

This is a new type of supplement recently marketed as a natural way to promote weight loss. There is limited evidence that taraxacum officinale, verbena officinalis, lithospermum officinale, equisetum arvense, arctostaphylos uva-ursi, arctium lappa and silene saxifraga infusion may affect diuresis in animals 282283. Two studies presented at the 2001 American College of Sports Medicine meeting 284285 indicated that although herbal diuretics promoted a small amount of dehydration (about 0.3% in one day), they were not nearly as effective as a common diuretic drug (about 3.1% dehydration in one day). Consequently, although more research is needed, the potential value of herbal diuretics as a weight loss supplement appears limited.

A number of nutritional supplements have been proposed to enhance exercise performance. Some of these nutrients have been described above. Table 3 categorizes the proposed ergogenic nutrients into apparently safe and effective, possibly effective, too early to tell, and apparently ineffective. Weight gain supplements purported to increase muscle mass may also have ergogenic properties if they also promote increases in strength. Similarly, some sports may benefit from reductions in fat mass. Therefore, weight loss supplements that help athletes manage body weight and/or fat mass may also posses some ergogenic benefit. The following describes which supplements may or may not affect performance that were not previously described. Based on this analysis, Table 4 summarizes the general nutritional recommendations for athletes and which dietary supplements may help power and endurance athletes.

Preventing dehydration during exercise is one of the keys of maintaining exercise performance (particularly in hot/humid environments). People engaged in intense exercise or work in the heat need to frequently ingest water or sports drinks (e.g., 1–2 cups every 10 – 15 minutes). The goal should be not to lose more than 2% of body weight during exercise (e.g., 180 lbs × 0.02 = 3.6 lbs). Sports drinks contain salt and carbohydrate. Studies show that ingestion of sports drinks during exercise in hot/humid environments can help prevent dehydration and improve endurance exercise capacity 43. Consequently, frequent ingestion of water and/or sports drinks during exercise is one of the easiest and most effective ergogenic aids.

General nutritional needs were discussed earlier. However, one of the best ergogenic aids available for active people is carbohydrate. Athletes and active individuals should consume a diet high in carbohydrate (e.g., 55 – 65% of calories or 5–8 grams/kg/day) in order to maintain muscle and liver carbohydrate stores 1. Additionally, ingesting a small amount of carbohydrate and protein 30–60 minutes prior to exercise and use of sports drinks during exercise can increase carbohydrate availability and improve exercise performance. Finally, ingesting carbohydrate and protein immediately following exercise can enhance carbohydrate storage and protein synthesis 1.

Earlier we indicated that creatine supplementation is one of the best supplements available to increase muscle mass and strength during training. However, creatine has also been reported to improve exercise capacity in a variety of events 54. This is particularly true when performing high intensity, intermittent exercise such as multiple sets of weight lifting, repeated sprints, and/or exercise involving sprinting and jogging (e.g., soccer) 54. Although studies evaluating the ergogenic value of creatine on endurance exercise performance are mixed, endurance athletes may also theoretically benefit in several ways. For example, increasing creatine stores prior to carbohydrate loading (i.e., increasing dietary carbohydrate intake before competition in an attempt to maximize carbohydrate stores) has been shown to improve the ability to store carbohydrate 286287288. Further, coingesting creatine with carbohydrate has been shown to optimize creatine and carbohydrate loading 289. Most endurance athletes also perform interval training (sprint or speed work) in an attempt to improve anaerobic threshold. Since creatine has been reported to enhance interval sprint performance, creatine supplementation during training may improve training adaptations in endurance athletes 290291. Finally, many endurance athletes lose weight during their competitive season. Creatine supplementation during training may help people maintain weight.

We previously mentioned that sodium phosphate supplementation may increase resting energy expenditure and therefore could serve as a potential weight loss nutrient. However, most research on sodium phosphate has actually evaluated the potential ergogenic value. A number of studies indicated that sodium phosphate supplementation (e.g., 1 gram taken 4 times daily for 3–6 days) can increase maximal oxygen uptake (i.e., maximal aerobic capacity) and anaerobic threshold by 5–10% 219220292293. These finding suggest that sodium phosphate may be highly effective in improving endurance exercise capacity. Other forms of phosphate (i.e., calcium phosphate, potassium phosphate) do not appear to possess ergogenic value.

During high intensity exercise, acid (H+) and carbon dioxide (CO₂) accumulate in the muscle and blood. One of the ways you get rid of the acidity and CO₂ is to buffer the acid and CO₂ with bicarbonate ions. The acid and CO₂ are then removed in the lungs. Bicarbonate loading (e.g., 0.3 grams per kg taken 60–90 minutes prior to exercise or 5 grams taken 2 times per day for 5-days) has been shown to be an effective way to buffer acidity during high intensity exercise lasting 1–3 minutes in duration 294295296297. This can improve exercise capacity in events like the 400 – 800 m run or 100 – 200 m swim 298. Although bicarbonate loading can improve exercise, some people have difficulty with their stomach tolerating bicarbonate as it may cause gastrointestinal distress.

Caffeine is a naturally derived stimulant found in many nutritional supplements typically as Gaurana, Bissey Nut, or Kola. Caffeine can also be found in coffee, tea, soft drinks, energy drinks, and chocolate. Studies indicate that ingestion of caffeine (e.g., 3–9 mg/kg taken 30 – 90 minutes before exercise) can spare carbohydrate use during exercise and thereby improve endurance exercise capacity 295299. People who drink caffeinated drinks regularly, however, appear to experience less ergogenic benefits from caffeine 300. Additionally, some concern has been expressed that ingestion of caffeine prior to exercise may contribute to dehydration although recent studies have not supported this concern 301302303. Caffeine doses above 9 mg/kg can result in urinary caffeine levels that surpass the doping threshold for many sport organizations. Suggestions that there is no ergogenic value to caffeine supplementation is not supported by the preponderance of available scientific studies.

Ingesting carbohydrate and protein following exercise enhances carbohydrate storage and protein synthesis. Theoretically, ingesting carbohydrate and protein following exercise may lead to greater training adaptations. In support of this theory, Esmarck and coworkers 93 found that ingesting carbohydrate and protein immediately following exercise doubled training adaptations in comparison to waiting until 2-hours to ingest carbohydrate and protein. Additionally, Tarnopolsky and associates 304 reported that post-exercise ingestion of carbohydrate with protein promoted as much strength gains as ingesting creatine with carbohydrate during training. These findings underscore the importance of post-exercise carbohydrate and protein ingestion.

As described above, glutamine has been shown to influence protein synthesis and help maintain the immune system. Theoretically, glutamine supplementation during training should enhance gains in strength and muscle mass as well as help athletes tolerate training to a better degree. Although there is some evidence that glutamine supplementation with protein can improve training adaptations, more research is needed to determine the ergogenic value in athletes.

Ingestion of 3–6 grams of EAA following resistance exercise has been shown to increase protein synthesis 848586878889909192. Theoretically, ingestion of EAA after exercise should enhance gains in strength and muscle mass during training. While there is sound theoretical rationale, it is currently unclear whether following this strategy would lead to greater training adaptations and/or whether EAA supplementation would be better than simply ingesting carbohydrate and a quality protein following exercise.

Ingestion of BCAA (e.g., 6–10 grams per hour) with sports drinks during prolonged exercise would theoretically improve psychological perception of fatigue (i.e., central fatigue). Although there is strong rationale, the effects of BCAA supplementation on exercise performance is mixed with some studies suggesting an improvement and others showing no effect 36. More research is needed before conclusions can be drawn.

HMB supplementation has been reported to improve training adaptations in untrained individuals initiating training as well as help reduce muscle breakdown in runners. Theoretically, this should enhance training adaptations in athletes. However, most studies show little benefit of HMB supplementation in athletes.

Ingesting glycerol with water has been reported to increase fluid retention 305. Theoretically, this should help athletes prevent dehydration during prolonged exercise and improve performance particularly if they are susceptible to dehydration. Although studies indicate that glycerol can significantly enhance body fluid, studies are mixed on whether it can improve exercise capacity 52306307308309310311.

Most research has evaluated the effects of ingesting ephedrine and caffeine (EC) supplements on weight loss. However, since ephedra and caffeine are stimulants and caffeine has been shown to have ergogenic properties, there has also been interest in the potential ergogenic value of EC. Recent research has shown that ingestion of low to moderate amounts of synthetic EC supplements generally improves endurance and high intensity exercise performance with no apparent adverse effects 312313314315316. However, it is unclear whether dietary supplements containing botanical ephedrine (i.e., ephedra) and caffeine (e.g., kola nut) have similar effects on performance. Further, since most sport organizations ban use of ephedrine the potential use in athletes appears limited.

MCT's are shorter chain fatty acids that can easily enter the mitochondria of the cell and be converted to energy through fat metabolism 317. Studies are mixed as to whether MCT's can serve as an effective source of fat during exercise metabolism and/or improve exercise performance 318319320321322.

Ribose is a 3-carbon carbohydrate that is involved in the synthesis of adenosine triphosphate (ATP) in the muscle (the useable form of energy). Clinical studies have shown that ribose supplementation can increase exercise capacity in heart patients 323324325326327. For this reason, ribose has been suggested to be an ergogenic aid for athletes. Although more research is needed, most studies show no ergogenic value of ribose supplementation on exercise capacity in health untrained or trained populations 328329330.

Inosine is a building block for DNA and RNA that is found in muscle. Inosine has a number of potentially important roles that may enhance training and/or exercise performance 331. Although there is some theoretical rationale, available studies indicate that inosine supplementation has no apparent affect on exercise performance capacity 332333334.

In addition to the supplements previously described, several nutrients have been suggested to help athletes stay healthy during intense training. For example, the American Medical Association recently recommended that all Americans ingest a daily low-dose multivitamin in order to ensure that people get a sufficient amount of vitamins and minerals in their diet. Although one-a-day vitamin supplementation has not been found to improve exercise capacity in athletes, it may make sense to take a daily vitamin supplement for health reasons. Glucosomine and chondroitin have been reported to slow cartilage degeneration and reduce the degree of joint pain in active individuals which may help athletes postpone and/or prevent joint problems 335336. Vitamin C, glutamine, Echinacea, and zinc have been reported to enhance immune function 42337338339. Consequently, some sport nutritionists recommend that athletes who feel a cold coming on take these nutrients in order to enhance immune function 42337338339. Similarly, nutrients such as vitamins E and C may help restore overwhelmed anti-oxidant defenses exhibited by athletes and reduce the risk of numerous chronic diseases 340. Creatine, calcium β-HMB, BCAA, and L-carnitine have been shown to help athletes tolerate heavy training periods 3674808183341342343344. Finally, omega-3 fatty acids, in supplemental form, are now endorsed by the American Heart Association for heart health in certain individuals 345. This supportive supplement position stems from: 1.) an inability to consume cardio-protective amounts by diet alone; and, 2.) the mercury contamination sometimes present in whole-food sources of DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) found in fatty fish. Consequently, prudent use of these types of nutrients at various times during training may help athletes stay healthy and/or tolerate training to a greater degree 37.