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When you’re trying to shed pounds and the scale isn’t moving in the right direction, it can be tempting to want to try something else, like a no-prescription weight loss supplement.

Some of those supplements are called "starch blockers" or "carbohydrate blockers." They may seem like a good option because they claim to keep starches, and the calories found in them, from being digested.

But it's not quite that simple. If you're thinking about trying them for weight loss, keep in mind that claims for these products are not based on reliable scientific evidence. However, if you're using them in conjunction with a good diet and exercise program, they may help you to lose weight.


What Are Starch Blockers?

Starches are complex carbohydrates that cannot be absorbed unless they are first broken down by the digestive enzyme amylase. Amylase inhibitors, also called starch blockers, prevent starches from being absorbed by the body.  When amylase is blocked, those carbs pass through the body undigested, so you don't absorb the calories.

Some starch blockers need a prescription. They are called acarbose (Precose), and miglitol (Glyset). These are used as treatments for blood sugar control in people with type 2 diabetes.

There are also starch blockers that are sold without a prescription as supplements.

What's the difference?

Prescription drugs have to prove to the FDA that they are safe and effective. Supplements don't. You also can't be sure of what's in a supplement.

Some supplements may have unlisted ingredients, maybe stimulants, that could be dangerous for people with diabetes, says Kathleen Dungan, MD, an endocrinologist at Ohio State University.

Prescription versions won’t have those extra ingredients, so they tend to be safer.

The FDA has sent warning letters to makers of no-prescription starch blockers in the past, saying their marketing claims are misleading.

If you're considering using any product marketed for weight loss, talk to your doctor or a dietitian first. Ask yourself if it sounds too good to be true, and be skeptical.

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