Effect of Diet versus Gastric Bypass on Metabolic Function in Diabetes

oshino et al. found that an 18% reduction in body weight improves insulin sensitivity similarly after gastric bypass or dieting in participants with obesity and type 2 diabetes. They conclude that their study results “challenge the current belief that upper gastrointestinal bypass has clinically meaningful effects on key metabolic factors involved in glucose homeostasis and the pathogenesis of diabetes that are independent of weight loss.” Nevertheless, in a recent article,1 the same research group reported that, after a 20% reduction in body weight, biliopancreatic diversion improved insulin sensitivity significantly more than gastric bypass. How do the authors reconcile these differing results? Furthermore, we note that the participants in the diet group in the study conducted by Yoshino et al. had less severe diabetes than those in the surgery group and appeared to use fewer medications, or no medications (mean [±SD] diabetes medication score [on a scale from 0 to 3.57, with a higher score indicating a greater number of medications, a higher dosage of medications, or both], 0.93±0.55 vs. 1.64±1.15).