Weight Loss Supplements

More than half of U.S. adults are overweight or obese, and more than one third of U.S. adults are trying to lose weight. Increasingly, they are turning to weight loss supplements for help. The most widely used weight loss supplement is ephedra. The active ingredients in ephedra- ephedrine alkaloids-are compounds with potentially powerful stimulant effects on the nervous and cardiovascular systems. The dietary supplement industry estimates that as many as 3 billion servings of ephedra are sold each year in the United States.

There is little evidence on whether weight loss supplements are efficacious. However, we identified several ways that weight loss supplements might cause health risks. Many weight loss supplements have been associated with side effects, some of which can be serious. Some weight loss supplements should be avoided by individuals with certain medical conditions because particular effects of the supplements could exacerbate the conditions. In addition, some weight loss supplements have potentially dangerous interactions with prescription or over-the-counter medications or foods. Further, a supplement may contain dangerous contaminants or different amounts of an active ingredient than indicated on the product label. Finally, we found multiple-ingredient products to be of particular concern because of the increased difficulty involved in evaluating and understanding their safety.

For most weight loss supplements, little scientific evidence to date supports their efficacy. Although there have been studies on specific ingredients, many of these studies have been of short duration, involved small numbers of individuals, or used study approaches that limited the usefulness of their findings. There have been few comprehensive reviews or long-term studies of efficacy. One comprehensive review of alternative treatments for weight loss found no reliable scientific evidence for the efficacy of any of the weight loss supplements that it reviewed. Another review found similar results except for ephedra. Most of the research that has been done to evaluate the efficacy of weight loss supplements has involved ephedra. A recently published randomized study found that a combination of ephedra and kola nut (a source of caffeine) promoted weight reduction. Other smaller studies have shown similar results for ephedra.

Further, research specific to weight loss supplements has not been a priority for federal agencies. There have been few systematic studies of weight loss supplements. Consequently, little is known about whether weight loss supplements are effective, but many of them have been reported to be associated with the potential for physical harm. However, as the upward trend in sales and use is expected to continue, more consumers may be at risk of adverse events related to use of the supplements. Consumers need scientifically accurate information about safety and efficacy to help guide their choices about weight loss supplements.

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