Harvard Health Letter

Ask the doctor: Bariatric surgery and diabetes

Q. I've heard bariatric surgery can reduce type 2 diabetes. How about type 1?

A. People who are obese are more likely to develop type 2 diabetes. People who are obese and already have type 2 diabetes find it easier to control their diabetes if they lose weight. The link between obesity and type 2 diabetes is strong, and bariatric surgery can lead to substantial weight loss. So you wouldn't be surprised if the surgery reduced the risk for type 2 diabetes. Nevertheless, in a recent study from Sweden, the magnitude of the benefit was remarkable. The researchers identified over 3,000 obese people without diabetes and followed them for 15 years. The risk of developing type 2 diabetes in those who received bariatric surgery was 83% lower than in those who didn't receive the surgery. There are different types of bariatric surgery, but they are all designed to reduce the absorption of calories in the intestine. That surely accounts for part of the weight loss seen following the surgery. However, we're now learning that the surgery also changes the levels of various hormones that affect appetite and metabolism, and that this also contributes to the weight loss—and possibly the reduced risk of developing type 2 diabetes. Most people with type 1 diabetes, which usually starts in childhood, are not obese. There is little reason to perform bariatric surgery in such patients. However, if a patient with type 1 diabetes is obese, and diet and exercise can't get the weight off, bariatric surgery could make sense. Type 1 diabetes greatly increases the risk of heart disease, and so does obesity. Bariatric surgery might not make type 1 diabetes easier to control, but it could help reduce the risk of heart disease.

—Anthony L. Komaroff, M.D.
Editor in Chief
Harvard Health Letter

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