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A Nutritionist's View: Just the Facts on Weight Loss Supplements: Where Is the Evidence?

Manore, Melinda M. Ph.D., R.D., FACSM


Get the facts with this overview of the most popular weight loss supplements on the market today and the research examining the effectiveness of these products.

Melinda M. Manore, Ph.D., R.D., FACSM, is chair and professor, Department of Nutrition and Food Management at Oregon State University, and is a member of the USA Gymnastics National Health Care Advisory Board and the Gatorade Sports Nutrition Advisory Board. Her research focuses on women's health issues, nutrition and exercise, energy balance and weight control, and disordered eating. Dr. Manore is an associate editor of ACSM's Health & Fitness Journal® and the author of Sport Nutrition for Health and Performance.

We are a nation struggling with a growing obesity problem and looking for a quick fix. For years, dietary supplements for weight loss have been a big business, with the sport nutrition and weight loss market topping $14 billion in 2003 (1). One of the most popular weight loss supplements has been ephedra (or Ma-huang), used either alone or with caffeine (2). Although research suggested that ephedra may help reduce body weight (1, 3), there were enough safety concerns related to ephedra use for weight loss that the Food and Drug Administration (FDA) pulled ephedra from the market in 2004 (4). Are there any weight loss supplements on the market that we can recommend to our clients? What does the research evidence indicate? This column will briefly discuss the most popular weight loss supplements on the market today and the research examining the effectiveness of these products. Only those products that have double-blind randomized clinical trials (RCTs) examining their effectiveness related to weight loss are discussed (2).

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Chitosan is a product produced from the exoskeleton of crustaceans with a structure similar to the dietary fiber cellulose (5). It has been promoted to reduce fat absorption, thus reducing total energy intake to bring about weight loss. Edzard Ernst, M.D., Ph.D., and Max H. Pittler, M.D. (6), performed an extensive meta-analysis of the research examining the effectiveness of chitosan for weight loss. In total, they examined 10 double-blind RCTs (2, 5) and found little evidence that chitosan reduced body weight in humans. The primary adverse effects were gastrointestinal distress and flatulence.

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Chromium Picolinate

Chromium is an essential trace element that, when bound to picolinate, enhances insulin activity (2, 5). Drs. Pittler and Ernst (2) reviewed 10 double-blind RCTs and found a small reduction in body weight (1.1 to 1.2 kg in 6 to 12 weeks; 0.08 to 0.2 kg per week) when compared with a placebo group after 6 to 14 weeks of supplementing in individuals with an average body mass index (BMI) of 28 to 33 kg/m2. In comparison, an approximately 1,200 kcal diet will result in weight loss of approximately 0.5 to 0.6 kg per week, depending upon the size of the individual and his or her activity level. Thus, the weight loss effect of chromium picolinate has little clinical relevance, although some studies may show statistically significant differences between treatment and placebo groups.



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Guar Gum

Guar gum is a dietary fiber that is derived from the Indian cluster bean and frequently added to processed foods to improve the texture of foods. Based upon the meta-analyses of Drs. Pittler and Ernst (2), 20 placebo-controlled RCTs have been conducted examining the effectiveness of guar gum in lowering body weight. These researchers pooled data using 11 of those studies, and found that guar gum was not effective in reducing body weight.

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Pyruvate is a 3-carbon compound that is generated in the body when glucose is metabolized. Manufactures advertise that pyruvate supplements will improve exercise performance and enhance body composition. Currently there are only two RCT studies that have examined the impact of pyruvate supplements on body composition in overweight individuals (BMI > 25) (2). Neither of these studies reported a greater reduction in body weight in individuals who used pyruvate versus a placebo. Thus, the evidence is weak that pyruvate supplements increase weight loss.

Numerous other weight loss supplements are on the market, including hydroxycitric acid, glucomannan, hydroxyl-methylbutyrate, plantago psyllium, yerbe mate, and yohimbe. These products have either no or limited RCT trials examining their effectiveness; thus, there are no data indicating, beyond a reasonable doubt, that one specific supplement will produce weight loss (2). Without any effective weight loss supplements on the market, the responsibility to educate your clients on diet and exercise for weight loss issues falls in your court. Helping your clients realize that weight loss is not a "quick fix," but a lifetime commitment to changing to a healthier lifestyle, may be the best weapon you have for fighting obesity.

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1. Nutrition Business Journal, Sports Nutrition and Weight Loss Report, 2004. Available at http://nbj/nbspornutwei.html. Accessed July 2004.
2. Pittler, M.H., and E. Ernst. Dietary supplements for body-weight reduction: a systematic review. American Journal of Clinical Nutrition 79:529-536, 2004.
3. Boozer, C.N., P.A. Daly, P. Homel, et al. Herbal ephedra/caffeine for weight loss: a 6-month randomized safety and efficacy trial. International Journal of Obesity 26(5):593-604, 2002.
4. Food and Drug Administration. Dietary Supplements Containing Ephedrine Alkaloids, Final Rule Summary. February, 2004. Available at Accessed July 2004.
5. Sarubin Fragakis, A. The Health Professional's Guide to Popular Dietary Supplements. 2nd ed. Chicago: American Dietetic Association, 2003.
6. Ernst, E., and M.H. Pittler. Chitosan as a treatment for body weight reduction? Perfusion 11:461-5, 1998.
© 2005 American College of Sports Medicine