A low-glycemic index diet combined with exercise reduces insulin resistance, postprandial hyperinsulinemia, and glucose-dependent insulinotropic polypeptide responses in obese, prediabetic humans.

Description

The aim of this study was to investigate the effects of combining exercise training with diets that vary only by glycemic index (GI) on glucose metabolism and insulin secretion in obese, prediabetic individuals. The study sample included 22 participants (mean±SEM age=66±1 years; body mass index=34.4±0.8 kg/m2) who underwent a 12-week exercise-training intervention (1 hour/day for 5 days/week at ≥85% of maximum heart rate) while randomly assigned to receive either a low-GI diet (LoGIX=40±0.3 arbitrary units) or a high-GI diet (HiGIX=80±0.6 arbitrary units). Results showed that similar weight loss (-8.8±0.9%) was achieved in both groups and this improvement was driven by decreases in whole-body fat mass and deep subcutaneous and intra-abdominal (visceral) adipose tissue. Moreover, no group differences were observed in insulin resistance between the 2 diets, but only individuals who consumed a low-GI diet presented a reduction in oral glucose-induced insulin secretion. In contrast, a high-GI diet increased the β-cell insulin secretory response to glucose when correcting for changes in insulin resistance. The beneficial reduction in insulin secretion in the LoGIX group was related to reduced postprandial gastrointestinal incretin responses. Thus, these results suggest that diet and exercise-induced improvements in body composition and insulin resistance in obese patients with prediabetes appears not to be influenced by dietary GI. However, the consumption of a high-GI diet impairs pancreatic β-cell function, while a low GI-diet decreases both hyperglycemia and hyperinsulinemia therefore relieving β-cell stress and preventing diabetes onset.