Have you seen advertisements claiming that you can lose weight by taking fat absorber pills that stick to fat in your intestines and prevent it from being absorbed into your bloodstream?

Any pill that prevents fat absorption can harm you. Of the 13 vitamins, four are fat soluble: vitamins A, D, E and K. That means that anything that blocks fat absorption blocks these four vitamins.

Fat absorber pills bind to small amounts of fat, but they cost about $35 to block the amount of fat in a Big Mac; in larger quantities they cause terrible gas and diarrhea.

Most of the fat blocker products are derived from chitin, a polysaccharide found in the exoskeleton of shellfish such as shrimp, lobster, and or crabs. Many sellers claim that chitin causes weight loss by binding fats in the stomach and preventing them from being digested and absorbed. Some refer to it as a “fat magnet” or “fat trapper.” Researchers at the University of California-Davis have demonstrated that chitin fat blocker products do not significantly block absorption of dietary fat (Obesity Research, Volume 11, 2003). At least three previously published studies have reached the same conclusion.

This study involved 15 men who consumed five meals per day for 12 days, with a total of about 25 grams of fat per meal. The amount of fat excreted during four days when they took fat-blocker capsules was then compared to the amount excreted during days without them. Taking 10 capsules of the product per day increased fecal fat excretion by only about one gram (a gram of fat is nine calories). This would have no significant effect on a person’s weight.

Thirty years ago starch blockers were the rage. You could buy pills that were supposed to prevent starch from being absorbed from your intestines into your bloodstream. Starch is normally broken down to sugars in your intestines and is absorbed into your bloodstream. If starch is not absorbed in your intestines, it passes to your colon where bacteria ferment it to cause gas and diarrhea. Since the starch blockers did not cause diarrhea, they did not prevent starch absorption and therefore do not help you to lose weight.

In a similar manner, if fat absorbers prevent fat from being absorbed, fat must pass out with your stool. This causes your stool to float. If you take fat blockers and your stool does not float, you know they are not working.

By Gabe Mirkin, M.D., for CBS Radio News
Checked 1/12/14