One method of reducing fat weight may be decreasing the amount of fat absorbed following digestion. Chitosan is a fiber supplement that is a form of chitin (a homopolymer of modified glucose) and is extracted from the shells of crustaceans. It has been marketed as an inhibitor of fat absorption. Chitosan can function in one of two ways: by binding bile acids and reducing their recycling, or 2) by delaying the digestion and blocking absorption of fat by binding to the fat in the intestine.
Most of the studies on Chitosan have been performed on animals. In those studies, Chitosan was primarily investigated as a hypocholesterolemic agent. Because Chitosan is supposed to reduce fat absorption, it would stand to reason that cholesterol levels would also be affected. Seven studies have been conducted in rats, and all seven report that Chitosan is effective in reducing blood cholesterol levels, especially when the rats consumed a high-fat diet. Whether a reduction in fat absorption results in a decrease in body fat has yet to be determined.
Only one study has investigated the effect of Chitosan in humans as a weight-reducing agent. Obese subjects were divided into one of three groups: placebo and two treatment groups. The treatment contained 240 mg of Chitosan, 55 mg of Garcinia cambogia (contains HCA), and 19 mg of chromium. The treatment groups received either one or two capsules. All three groups were required to consume a hypocaloric diet, about 100 kcals. The authors reported that the dietary supplement containing Chitosan and HCA in conjunction with a hypo caloric diet can achieve a greater reduction in weight that is dose dependent Furthermore, subjects experienced a significant reduction in total cholesterol and LDL and triglycerides, and a significant elevation in HDL.
Although this study shows positive results, Chitosan alone has not been determined to be effective as a fat-loss product. However, when combined with HCA, it appears to promote fat loss. Additional research should be conducted to verify these results and to determine any effects of these substances in isolation.
Safety and Toxicity
Chitosan seems to be effective in reducing lipid digestion and absorption. However, when fat absorption is inhibited, the fat is eliminated in the feces. The most common side effect associated with products inhibiting fat absorption is diarrhea. Other documented side effects include a reduction in calcium absorption and a reduction in the absorption of fat-soluble vitamins, especially vitamin E. Deuchi et al. reported that the decrease in calcium absorption was enough to reduce bone mineral content of rats in just 2 weeks of treatment.
Animal studies also indicate that Chitosan may decrease Bifidobacterium and lactobacillus. These are bacteria that are normally found in the intestinal tract, which have important roles including the regulation of digestion and vitamin manufacture and release. Therefore, it would be necessary for vitamin and mineral supplementation during the consumption of Chitosan supplements.