Reprinted from Eating Disorders Review
May/June 2003 Volume 13, Number 3
©2002 Gürze Books
“Fat blockers” are a staple of late-night television and radio. Chitosan, frequently touted on radio and television as an “effective fat blocker,” is a derivative of the polysaccharide chitin found in the shells of invertebrates such as shrimp and crabs. The manufacturer claims that chitosan blocks absorption of as much as 120 g of dietary fat per day and, as a result, promotes weight loss. However, when a team of researchers at the University of California, Davis, tested this claim, chitosan failed completely.
Because dietary fat that is not absorbed must be excreted in the feces, the researchers assessed the product’s effectiveness by measuring fecal fat excretion among seven healthy male volunteers (Int J Obesity 2001; 26:119). The men, who were 23 to 30 years of age, with an average body mass index of 26, maintained a high fat intake (more than 120 g/day) for 12 days. On days 6-9, they took chitosan before meals and snacks, exactly as directed by the manufacturer. A charcoal marker was consumed on days 2, 6, and 10 to mark the baseline and supplement periods.
Fecal fat was unchanged
The product did not increase fecal fat content and therefore did not block fat absorption. In two other trials, chitosan taken for 4 and 8 weeks without restricting energy intake failed to increase weight loss over placebo (Eur J Clin Nutr 1999; 53:379 and Meth Findings Exp Clin Pharmac 1999; 21:357). The authors note that their study illustrates the importance of using clinical research to evaluate the efficacy of dietary supplements, most of which are not regulated.