Often marketed as a natural weight loss aid, chitosan is a dietary supplement made from the shells of crustaceans (such as crabs, shrimp, and lobster). Although supplement manufacturers claim that chitosan can fight fat absorption, there is little scientific support for the weight loss benefits of chitosan.
The Science Behind Chitosan and Weight Loss
For a report published in the Cochrane Database of Systematic Reviews in 2008, researchers reviewed 15 clinical trials (with a total of 1,219 participants) that tested the effects of chitosan on adults who were overweight or obese. Compared to participants given a placebo, study members treated with chitosan appeared to lose significantly more weight and experience beneficial changes in cholesterol levels and blood pressure. However, the report's authors note that many of the reviewed trials were of poor quality. Furthermore, findings from the high-quality trials suggest that chitosan may have a minimal, insignificant effect on weight.
A larger report (published in the American Journal of Clinical Nutrition in 2004) also indicates that chitosan may not be useful for weight loss. Looking at five previously published reviews and meta-analyses (as well as 25 additional clinical trials), the report's authors found "no evidence beyond a reasonable doubt that any specific dietary supplement is effective for reducing body weight." Supplements highlighted in the report included chitosan, yerba mate, and yohimbe.
Should You Use Chitosan for Weight Loss?
Due to the lack of scientific support for its use, chitosan cannot be recommended for weight loss. What's more, some research shows that chitosan may cause certain adverse effects (including constipation and upset stomach) and reduce absorption of essential nutrients (including calcium and vitamins A, D, E, and K). In addition, chitosan may cause allergic reactions in people with shellfish allergies.
In order to lose weight, it's important to follow a healthy diet (including a wide variety of vegetables and fruits and a limited intake of saturated fats and refined-grain products) and stick with an exercise program that combines aerobic activity with strength training. Improving your sleep hygiene and managing your stress levels may also help promote weight loss.
Jull AB, Ni Mhurchu C, Bennett DA, Dunshea-Mooij CA, Rodgers A. "Chitosan for overweight or obesity." Cochrane Database Syst Rev. 2008 Jul 16;(3):CD003892.
Memorial Sloan-Kettering Cancer Center. "About Herbs: Chitosan". March 2009.
Mhurchu CN, Dunshea-Mooij C, Bennett D, Rodgers A. "Effect of chitosan on weight loss in overweight and obese individuals: a systematic review of randomized controlled trials." Obes Rev. 2005 Feb;6(1):35-42.
Pittler MH, Ernst E. "Dietary supplements for body-weight reduction: a systematic review." Am J Clin Nutr. 2004 Apr;79(4):529-36.