Exercise training and dietary glycemic load may have synergistic effects on insulin resistance in older obese adults.

BACKGROUND/AIMS The aim of this study was to assess the combined effects of exercise and dietary glycemic load on insulin resistance in older obese adults. METHODS Eleven men and women (62 +/- 2 years; 97.6 +/- 4.8 kg; body mass index 33.2 +/- 2.0) participated in a 12-week supervised exercise program, 5 days/week, for about 1 h/day, at 80-85% of maximum heart rate. Dietary glycemic load was calculated from dietary intake records. Insulin resistance was determined using the euglycemic (5.0 mM) hyperinsulinemic (40 mU/m(2)/min) clamp. RESULTS The intervention improved insulin sensitivity (2.37 +/- 0.37 to 3.28 +/- 0.52 mg/kg/min, p < 0.004), increased VO(2max) (p < 0.009), and decreased body weight (p < 0.009). Despite similar caloric intakes (1,816 +/- 128 vs. 1,610 +/- 100 kcal/day), dietary glycemic load trended towards a decrease during the study (140 +/- 10 g before, vs. 115 +/- 8 g during, p < 0.04). The change in insulin sensitivity correlated with the change in glycemic load (r = 0.84, p < 0.009). Four subjects reduced their glycemic load by 61 +/- 8%, and had significantly greater increases in insulin sensitivity (78 +/- 11 vs. 23 +/- 8%, p < 0.003), and decreases in body weight (p < 0.004) and plasma triglycerides (p < 0.04) compared to the rest of the group. CONCLUSION The data suggest that combining a low-glycemic diet with exercise may provide an alternative and more effective treatment for insulin resistance in older obese adults.