Starch Blockers

Claims, Benefits: Eat all you want and still lose weight.

Bottom Line: There are no human studies to back up the claims. Any effect is likely to be small.

Full Article, Wellness Letter, February 2005

Q: Are starch-blocking pills a safe and effective way to diet?

A: No. These products, such as Carb Crusher, Starch Away, and Slender Now System, claim that you can eat all you want and still lose weight—provided you take these pills, at a cost of $50 to $100 a month. The idea is that the pills block starch digestion. For example, if you ate cereal containing 240 calories and took a starch blocker, you’d absorb only 26 of the calories, or so the sellers claim. The pills usually contain an extract of white kidney beans, a protein compound that blocks an enzyme in the intestine (alpha amylase) and keeps it from breaking down starch, as it normally would do. Thus, in theory, the starch passes into your large intestine and is excreted.

Manufacturers cite lab studies to support their claims, but no human studies on these products have yet been published—and most investigators are involved financially with the manufacturers. The idea of starch-blocking may sound logical—and it’s impossible to say that the pills have no effect at all. But the protein in the pill, or most of it, is itself probably digested before it can block anything. Starch digestion begins in the mouth, and continues in the small intestine. Another problem: the body is likely to produce more alpha amylase than a pill could block. Still another is that undigested starch in your large intestine would cause gas, bloating, abdominal pain, and diarrhea. Customers who complain of such symptoms are told it’s a sign that the pills work.

Starch blockers are nothing new—the FDA took several such products off the market in the 1980s. There actually is an FDA-approved prescription drug (acarbose, brand name Precose) that does slow starch digestion. It is used only for people with diabetes as a means of blocking a rapid rise in blood sugar. Its effects are moderate, and it does not lead to weight loss. Side effects include gas and diarrhea.

No one, particularly people with diabetes, should take starch blockers sold over the counter.

UC Berkeley Wellness Letter, February 2004