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Study Casts Doubt on Weight Loss Supplements

Researchers Say 9 Dietary Supplements Are Not Effective for Cutting Weight
By
WebMD Health News
Reviewed by Laura J. Martin, MD

July 12, 2010 -- Those expensive dietary supplements that promise dramatic weight loss by trapping fat, blocking carbs, or boosting metabolism work no better than placebo pills, a new study shows.

Researchers in Germany tested nine such products against placebo pills in one of the most extensive trials of weight loss supplements ever conducted.

They found that the supplements were no more effective than the dummy pills for promoting weight loss during the eight-week study.

The investigators say the findings show the importance of subjecting supplements marketed for weight loss to rigorous scientific research to determine if they have any benefit.

The study was presented today in Stockholm at the International Congress on Obesity.

Billions Spent on Weight Loss Supplements

Europeans spend about $1.4 billion a year on unregulated weight loss supplements and Americans spend about $1.6 billion a year on the products, researcher Igho Onakpoya, MSc, says.

In a review of the limited research on the dietary supplements, Onakpoya and colleagues from the universities of Exeter and Plymouth in the U.K. found little evidence that any of the widely sold, unregulated products they tested promoted weight loss.

"The only thing these supplements effectively help people lose is their money," Onakpoya tells WebMD.

The only tested supplements found to promote weight loss were those containing ingredients shown to pose a health risk, such as ephedra, which was banned in the U.S. in 2004 following a series of heart-related deaths linked to products containing the stimulant.

Study Included So-Called 'Fat Blockers'

The nine weight loss supplements tested in the German study included the active ingredients L-carnitine, polyglucosamine, cabbage powder, guarana seed powder, bean extract, Konjac extract, fiber, sodium alginate, or selected plant extracts either alone or in combination.

These ingredients have been marketed for promoting weight loss in a number of ways. Guarana seed, which is found in many of the weight loss supplements sold over the counter in the U.S., is said to be an appetite suppressant and energy booster. L-carnitine is said to promote muscle growth while burning fat.

The polyglucosamine protein chitosan, which is commonly derived from the shells of crabs, shrimp, and other shellfish, is also a popular ingredient in weight loss supplements. Products containing chitosan are generally marketed as dietary fat blockers.

Study researcher Thomas Ellrott and colleagues from Germany's University of Gottingen Medical School enrolled 189 obese or overweight middle-aged people who agreed to take a weight loss supplement for eight weeks. Half took commercially available supplements and half took the dummy pills.

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