No Meaningful Difference in Weight Loss
The over-the-counter supplements were purchased from area pharmacies, but the researchers changed their packaging and product names to make them indistinguishable from the placebo pills.
Some of the products included dietary advice in their instructions, so the researchers rewrote the instructions to include the advice without mentioning the product name.
After eight weeks, people taking the commercial supplements had lost an average of 2 to 4 pounds compared to an average loss of 2 and 1/2 pounds in the placebo group, but the difference could have been a chance finding.
Weight loss supplements like the ones tested in the study are not regulated and their claims do not have to be proven in clinical trials.
The research was supported by funding from the German consumer magazine Justice. No other funding sources were reported.
Researcher: 'Buyer Beware'
Weight loss supplement researcher Judith Stern, ScD, tells WebMD that she knows of no unregulated supplements that promote weight loss and keep weight off.
She says studies of several years' duration would be needed to prove the effectiveness of a dietary supplement or drug marketed for weight loss.
"If you tell someone a pill will help them lose weight and you motivate them to do it, many people will lose weight," she says. "But it is impossible to know if the pill caused the weight loss."
Stern's own research examining chitosan-containing supplements found no support for the claim that the products "trap" dietary fat and excrete them from the body.
"If these supplements worked I would be the first person to recommend them," she says. "But the claims on the labels are just that and the manufacturers don't have to prove them. My message to the public is caveat emptor: Let the buyer beware."
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.