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Can Starch Blockers Help You Lose Weight?

A closer look at the promise of guilt-free carb consumption.
WebMD Feature

Some dieters are tempted to turn to dietary supplements called starch blockers to try to sidestep carb calories. But do these products deliver? Here's what experts told WebMD.

Also called carb blockers, starch blockers contain an extract called phaselous vulgaris, which comes from white kidney beans. Makers say that by blocking a starch-digesting enzyme called alpha-amylase, starch blockers prevent the body from absorbing carbs -- sparing you from the carb calories.

Supplements, Not Drugs

Starch blockers aren't the same as the prescription drug Precose, used in some people with type 2 diabetes to slow starch absorption for blood sugar control. Precose is not used for weight loss.

Starch blockers are dietary supplements, not prescription drugs. Since they don't go through the FDA's drug approval process, the FDA has not signed off on whether starch blockers -- or any other supplements -- are safe, effective, or contain what the label says is in the bottle.

“The manufacturer is responsible for marketing a safe product,” FDA spokeswoman Siobhan DeLancey, RVT, MPH, tells WebMD. 

WebMD contacted the Council for Responsible Nutrition (CRN), a trade group for the dietary supplements industry, representing dietary supplement manufacturers and ingredient suppliers, for its response.

In a written statement, Duffy MacKay, ND, CRN's vice president for scientific and regulatory affairs, tells WebMD that, in general, studies show that "extracts of phaseolus vulgaris appear to be safe and have potential promise" to help overweight or obese people lose weight. But further studies with more people in them are needed to confirm that, MacKay notes.

What the Experts Say

Starch blockers probably do allow complex carbohydrates to pass through the small intestine largely undigested, says Christine Gerbstadt, MD, RD, an American Dietetic Association spokeswoman.

“But when they get to the large intestine, the starches ferment, give off gas, and cause bloating and diarrhea,” Gerbstadt tells WebMD.

Gerbstadt says she doesn't recommend using starch blockers because there haven't been enough tests done in people showing that the products help.

Obesity expert Louis Aronne, MD, says his patients usually don't stick with starch blockers for long.

“We just don’t see people taking stuff like this on an ongoing basis. When patients come in taking a carb blocker, they end up stopping either because of the side effects or because of lack of effectiveness, or both,” says Aronne, who directs the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Center.

MacKay stresses that it's important not to rely only on supplements for weight loss. As he puts it, those products "are not magic bullets," and a healthy diet and exercise are also needed for successful weight loss.

 "If something sounds too good to be true, it probably is,” MacKay writes.

Focus on Fiber Instead

If you’re going to take a supplement for weight loss, Gerbstadt suggests taking a fiber supplement instead.

According to the American Dietetic Association, people who get 20 to 27 grams of daily fiber from fruits, vegetables, whole grain, legumes, or up to 20 grams from dietary supplements are more likely to be successful in controlling their weight compared to those who don’t.

Studies also show that a high-fiber diet makes you feel fuller, less hungry, and is more satisfying to the appetite.

If you’re thinking about taking any dietary supplement, do your homework. The National Center for Complementary and Alternative Medicine, which is part of the National Institutes of Health, recommends getting reliable research about the product and telling your doctor about any supplements you take.

Reviewed on July 02, 2010

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