Chitosan is a naturally occurring fiber derived from the complex sugar (polysaccharide) found in the shells (exoskeletons) of shrimp, crabs and other shellfish. Chitosan has the capacity to bind lipids and fats. More importantly, since it is not digested, chitosan has no calories.

Upon oral ingestion, chitosan binds to the intestinal lining, where it tightly binds dietary fats and lipids before they are absorbed in the body. As a result, the dietary fat is prevented from entering into the bloodstream. When dietary fat is bound to the chitosan fiber, it becomes a large mass, which cannot be absorbed in the body.

Published reports have shown that chitosan works in concert with vitamin C. It has been suggested that the action of chitosan may be enhanced by as small an amount of vitamin C as 10 mg. Used alone, ingestion of 500 mg chitosan before a meal rich in fat helps reduce "bad" (LDL) cholesterol. The "bad" cholesterol is bound to bile acids secreted by the liver into the intestine, where its reabsorption is prevented by chitosan fibers.