Thursday, November 04, 2004

Chitosan: Is It Good for Weight Loss?

The product and what it's marketed for: chitosan is a dietary fiber derived from the shells of shrimp, crabs and other crustaceans. Many companies promote it as a weight-loss tool, a natural "fat-blocker." The fiber is packaged into a pill that, when taken just before eating, is said to bind to fat in your food, causing the grease you ate to be excreted rather than absorbed.

Many brands claim that, in addition to taking off the pounds, chitosan boosts HDL, good cholesterol, while reducing the bad, LDL cholesterol, and decreases the risk of colon cancer. Different companies market pills with different dosages and distinguish their products with different formulations, often adding vitamin C or other compounds that they claim improve chitosan's fat binding ability.

Depending on the formulation, marketers claim the supplement can absorb as much as 12 times its own weight. Some brands are advertised online for as low as $5; others cost $40 or more and most bottles last 1 to 2 months, depending on how many pills are taken at a time and how frequently.

Whats's known: chitosan binds to fatty acids - which are what's left of the fat in your food after your stomach enzymes have broken it down. Theoretically, that fat is then shuttled out of your system attached to the indigestible fiber.

Scientific studies are often cited as proof of chitosan's effectiveness in the promotional literature, but the few studies that have shown chitosan to be effective for weight-loss are "flawed in many ways," said Max Pittler, a researcher in complementary medicine at the Universities of Exeter and Plymouth in the United Kingdom. Pittler worked on a clinical study, which was published in a peer-reviewed journal in 1998, and found the supplement had no effect on weight or cholesterol.

Clinical studies have failed to prove that chitosan actually helps you slim down, but a few have shown that it can moderately curb cholesterol levels, said pharmacologist Richard Ogletree at the University of Mississippi Medical Center in Jackson and the co-author of "The Physicians' and Pharmacists' Guide to the Top Ten Scientifically Proven Natural Products." Ogletree said he wouldn't recommend chitosan to someone looking to lose weight, but if someone was set on taking the supplement, he wouldn't be too discouraging. Unless you are allergic to shellfish, in which case it might spark a reaction, chitosan doesn't seem to have dangerous side effects, and, he added, "most people can use a little decrease in cholesterol."

There have been no clinical studies testing whether different formulations of chitosan are more effective, Ogletree said. Based on its chemistry, vitamin C ought to help it work better. Still, even at its most effective, chitosan will likely do as much to reduce cholesterol as oat bran and other soluble fibers. A more cost-effective approach to heart health would be to eat more oatmeal. And neither option is dramatic enough for those with dangerously high cholesterol.

The Bottom Line: No supplement is likely to ever help you drop pounds if you don't change your eating and exercise habits, experts say.

"It's not easy to lose weight," said Jyni Holland, a dietician at New York University Medical Center. "It requires work and dedication."

The surest way to slim down is to eat fewer calories and do moderate exercise. Holland recommends setting realistic goals, keeping nutritious, low-calorie foods close at hand and using your willpower to stay away from waist-expanding foods such as pizza or potato chips. "If losing weight were easy, no one would be obese."

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