Cutting Out the Middleman: Another Benefit of Gastric Bypass
A new study indicates that bypass surgery may do more for people with diabetes than just helping them shed pounds.
Researchers compared blood glucose levels from people with type 2 who lost weight with bypass surgery to those who lost the same amount of weight on a low-calorie diet. In the study, the surgery patients’ blood glucose dropped lower after a glucose drink than the dieters’ did, indicating that their bodies were doing a better job of processing the sugar than the low-cal group’s were. This improvement in blood glucose control may stem from the surgery’s trademark digestive redesign. “The idea is to bypass part of the gut so the nutrients are not exposed to all of the gut, so there is minimal absorption,” says the study’s lead author, Blandine Laferrère, MD, an assistant professor of medicine at Columbia University.
Gastric bypass is different from lap-banding, another type of weight-loss surgery that cinches the stomach with a belt. Lap-banding generated a lot of buzz earlier this year after a study found that 75 percent of patients with type 2 diabetes went into diabetic remission after lap-banding, compared to just 10 percent of those pursuing non-surgical weight loss. The gap in remission rate was attributed to the greater weight loss from lap-banding compared to dieting. But, in bypass surgery, the new study suggests that weight loss alone doesn’t tell the whole story.
Instead, the outcome may be due to a surge in a process called the “incretin effect.” As food meanders its way through the digestive tract, gut cells release hormones called incretins. Those incretins travel through the blood and, when they reach the pancreas, trigger the secretion of insulin, which brings blood glucose down. The incretin process is known to be dampened in people with type 2 diabetes. But it looks like gastric bypass surgery can, at least partially, repair this defect: Laferrère and her colleagues measured an increase in incretin levels in the bypass patients, but not in the dieters. “Many people have shown that incretin levels go up after gastric bypass and not gastric banding,” says Laferrère. But this is the first study to rule out weight loss as the cause for that boost in incretins.
Laferrère notes that the details of how bypass surgery increases incretin flow are not well understood. But when it comes to her own patients, she says, “I’ve changed a lot myself over 10 years. When I was fresh out of my training, I would not speak about the surgery in the first visit. Now, I do.”
This study was published online Apr. 22, 2008, in the Journal of Clinical Endocrinology and Metabolism.