The dietary supplement chitosan shows some promise in treating overweight and obesity but has not been shown conclusively to be an effective weight loss aid, according to a new systematic review of current evidence.

The review assessed results of 14 randomized controlled trials that included 1,131 overweight or obese adults. Those who received chitosan (pronounced kigh-toh-san) had an average weight loss of almost 4 pounds more than those on placebo in the short term, and their cholesterol and blood pressure levels also decreased more than those in the placebo group. There were no side effects noted in the group taking chitosan.

“This review has indicated that chitosan may be an effective aid to weight loss but many of the included trials have been limited by poor methodology and reporting,” according to lead author Cliona Ni Mhurchu, Ph.D., of the University of Auckland in New Zealand, and colleagues.

According to the background information from the National Institute of Environmental Health Sciences, Chitosan (marketed also as chitopearl and chitin) was popularized as a weight loss aid by the 1997 book The Fat Blocker Diet. The supplement is derived from chitin, which is found the in the shells of shrimp, lobster and crab.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. 

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