Effects of a Carbohydrate-Restricted Diet on β-Cell Response in Adults With Type 2 Diabetes

Abstract Context β-Cell response to glucose is compromised in individuals with type 2 diabetes (T2D), possibly due in part to excessive carbohydrate consumption. Objective This study was conducted to determine if a eucaloric carbohydrate-restricted (CR) diet (∼9% energy from carbohydrate, 65% energy from fat), compared to a eucaloric higher carbohydrate (HC) diet (∼55% energy from carbohydrate, 20% energy from fat), would improve β-cell response to glucose in participants with T2D. Methods Participants were 57 African American and European American adults with T2D not using insulin. Medications were discontinued 1 to 2 weeks prior to baseline testing. A hyperglycemic clamp was used to assess the acute (first-phase) and maximal (arginine-stimulated) C-peptide response to glucose at baseline and after 12 weeks of controlled diet therapy (all food provided). An oral glucose tolerance test (OGTT) was used to assess the disposition index (DI). Results At 12 weeks, a statistically significant effect of diet was observed on acute C-peptide response (2-fold greater with the CR diet; P < .01). For maximal C-peptide, a significant effect of diet was observed (22% greater with the CR diet; P < .05), as was a significant diet-by-race interaction (P < .05), indicating that the diet effect was specific to European Americans (48% greater with the CR diet; P < .01). OGTT results showed a significant effect of diet on DI at 12 weeks (32% greater with the CR diet; P < .05). Conclusion These results suggest that a eucaloric CR diet has beneficial effects on β-cell function in patients with mild T2D.