Elucidating the Mechanisms Behind the Restoration of Euglycemia After Gastric Bypass Surgery

According to the U.S. Centers for Disease Control and Prevention (CDC), in the United States in 2010, 78 million adults were obese, 79 million had prediabetes, and 26 million had diabetes. Bariatric surgery in obese persons has been shown to be an effective method for resolving and preventing type 2 diabetes (1,2). However, not all bariatric surgery is the same. After gastric banding, where the amount of food consumed is limited by an inflatable band around the cardia of the stomach, the improvement seen in diabetes is associated to the amount of weight lost (3). In contrast, after Roux-en-Y gastric bypass (RYGB) surgery—where most of the stomach, duodenum, and the first 40 cm of the jejunum are bypassed and nutrients enter directly into the jejunum—an improvement in diabetes occurs a few days after surgery, before any weight has been lost (4). It was recently demonstrated in a randomized trial that gastric bypass is more effective than medical treatment in resolving diabetes in patients with a BMI starting at 27 kg/m² (5). This raises the possibility that more patients with diabetes will undergo bariatric surgery in the future.

Several mechanisms have been proposed for this early improvement in glycemic control seen after gastric bypass (Fig. 1). These include, but are not limited to, improvements in hepatic insulin sensitivity …