Patients with type 2 diabetes who undergo bariatric surgery often see a huge drop in blood sugar levels that doctors long believed was due to the operation. But new research suggests it’s actually the very low-calorie diets patients are required to follow after bariatric surgery that lead to the known improvements in diabetes.
"For years, the question has been whether it is the bariatric surgery or a change in diet that causes the diabetes to improve so rapidly after surgery," said Ildiko Lingvay, M.D., an assistant professor of internal medicine at the University of Texas Southwestern Medical Center who helped conduct the study published online in the journal Diabetes Care. "We found that the reduction of patients' caloric intake following bariatric surgery is what leads to the major improvements in diabetes, not the surgery itself."
The study followed 10 patients who were initially treated only with the standard low-calorie diet given to patients after bariatric surgery, while researchers measured effects on blood glucose levels. Several months later, the patients underwent the Roux-en-Y gastric bypass bariatric surgery and followed the same diet and were again tested for blood glucose levels.
Patients received less than 2,000 calories total during each of these 10-day periods, which is the customary diet after gastric bypass surgery.
Fasting blood glucose levels dropped 21 percent on average during the diet-only phase, and 12 percent with the surgery-diet combo. Patients' blood glucose levels after a standard meal decreased by 15 percent in the diet-only phase and 18 percent after surgery-plus-diet. The scientists said the results demonstrate that the extremely restrictive diet imposed after bariatric surgery is responsible for the rapid diabetes remission, which occurs within days of the procedure.
"Unfortunately, such a restrictive diet is nearly impossible to adhere to long-term in the absence of bariatric surgery," Dr. Lingvay said. "We found that the success of bariatric surgery is mediated through its ability to control food intake, which in turn has a beneficial effect on diabetes."
Type 2 diabetes often develops as a result of obesity. The American Diabetes Association estimates that more than 20 million people in the U.S. have type 2 diabetes. If left untreated, the diabetes can lead to other conditions such heart disease and stroke, as well as nerve and kidney damage.
The study was funded, in part, by the National Institutes of Health.
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