The idea of taking a pill that blocks the fat a person eats has great appeal. Fat blockers purport to block the absorption of fat, allowing ft to pass through the body without hanging on the hips. Prescription medications that block fat do work, but over-the-counter supplements have not been tested in clinical trials. Whether fat blocker supplement claims have any validity remains an unanswered question.
Alli
Alli, an over-the counter supplement that claims to block fat, is a lower dose of orlistat, a medication approved by the Food and Drug Administration for weight loss. Prescription orlistat, sold as Xenical, contains 120mg. of orlistat, compared to 60mg. in Alli. Orlistat blocks the action of the enzyme lipase, which helps to break down dietary fat in the intestine. Since lipase doesn't break down the fat, fat passes through the intestine and exits the body in the stool. People taking Alli should eat no more than 15 grams of fat with each meal, because side effects such as diarrhea, urgency and uncontrollable gas with involuntary passage of oily spots. The weight loss expected with Alli is based on expected loss on Xenical, which normally results in only 5 to 7 lbs. weight loss over a year, with most weight lost in the first six months, the Mayo Clinic states. Alli can cause loss of fat-soluble vitamins, so people taking Alli should also take a multivitamin.
Chitosan
Chitosan, made from crustacean shells, is a popular ingredient in over-the-counter supplements claiming to block fat absorption. The shells are indigestible, so they pass through the body without being absorbed. Proponents claim that the shells absorb dietary fat and carry it out of the body unabsorbed. Two studies have not validated these claims, which showed no increase in weight loss over placebos, nutritionist Dr. Barbara Struempler of the Alabama Cooperative Extension System states. While a small amount of fat may bind to chitosan, the amount isn't large enough to affect weight loss. Using the supplement may decrease fat-soluble vitamin A and D levels.
Soluble Fiber
Soluble fiber, sometimes combined with chitosan in fat blocker supplements, can lower cholesterol levels and aids in weight loss by making a person feel fuller due to the bulk, the Mayo Clinic reports. Soluble fiber may also block fat absorption in the intestine, NYU Langone Medical Center states.
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