Fat Loss Aids: Chitosan is an indigestable fiber that is obtained from the shells of shellfish. It is often used as a fat blocker because of its lipophilic properties (it is attracted to fat). When taken before a meal, chitosan supposedly binds to dietary fat so that it can be eliminated undigested along with the chitosan. This makes chitosan popular for losing weight and lowering cholesterol levels, and it is included in many weight loss formulas.
Unfortunately, there is just about zero supporting evidence for the effectiveness of chitosan in blocking fat absorption in humans, while there is a lot of evidence against its effectiveness. While it has been found that chitosan has the ability to lower cholesterol in animals, (1, 5) multiple human studies have found that its fat blocking effects are at most insignificant. (2, 3, 4)
I suppose that this is one of those supplement ingredients that looks great on paper, yet fails to deliver in real world situations. Perhaps the best way to manage dietary fat absorption is to control its intake in the first place. In this stiuation supplements like chitosan, even if it did work, would be of no use anyways.
1. Zhang J, Liu J, Li L, & Xia W. (2008). Dietary chitosan improves hypercholesterolemia in rats fed high-fat diets. Nutrition Research (New York, N.Y.). 28(6), 383-90.
2. Gades MD, & Stern JS. (2005). Chitosan supplementation and fat absorption in men and women. Journal of the American Dietetic Association. 105(1), 72-7.
3. Gades MD, & Stern JS. (2003). Chitosan supplementation and fecal fat excretion in men. Obesity Research. 11(5), 683-8.
4. Gades MD, & Stern JS. (2002). Chitosan supplementation does not affect fat absorption in healthy males fed a high-fat diet, a pilot study. International Journal of Obesity and Related Metabolic Disorders : Journal of the International Association for the Study of Obesity. 26(1), 119-22.
5. Gallaher CM, Munion J, Hesslink R Jr, Wise J, & Gallaher DD. (2000). Cholesterol reduction by glucomannan and chitosan is mediated by changes in cholesterol absorption and bile acid and fat excretion in rats. The Journal of Nutrition. 130(11), 2753-9.