I Didn’t Know That . . .

Q: Do the so-called fat blockers such as chitin and chitosan actually work?

A: No, according to medical experts. These tablets, made most often from the shells of crustaceans, are supposed to bind tightly to fats in the diet, sweeping them through the intestines so they are not digested. But there have been almost no studies to demonstrate whether they work. The only reliable study of their effects, published recently in the British journal Perfusion, showed no weight loss in the group consuming chitin. If they did work as claimed, moreover, experts say they would produce diarrhea (because of the extra fat in the stool) and strip fat-soluble vitamins from the intestines, as does the artificial fat Olestra. There is no evidence that this occurs. The Federal Trade Commission won a major lawsuit against one manufacturer last year for making false advertising claims, and the district attorneys of Napa and Sonoma counties have filed suit against five other makers, charging deceptive advertising.