The effects of 12 wk of physical training in addition to hypocaloric diet (DPT group, N = 10) on body composition, carbohydrate (CHO) tolerance, and insulin secretion and action were compared with the effects of diet therapy alone (D group, N = 8) in CHO-intolerant and non-insulin-dependent diabetic subjects.

Fat mass, fat-free mass (FFM), mean fasting plasma glucose, serum C-peptide, and insulin concentrations decreased similarly in both groups. The mean plasma glucose response to a mixed meal decreased approximately 20% in both treatment groups, and, after i.v. glucose, decreased 12% in the D group (P < 0.05), but did not change in the DPT group (NS between groups). The acute serum insulin response (0–6 min) after IG increased significantly in the DPT group only (NS between groups).

The mean basal endogenous glucose production (BEGP) decreased 17% (P < 0.025) in the DPT group and by 31% (P < 0.01) in the D group (NS between groups). Hepatic sensitivity to insulin, estimated by BEGP suppression during the euglycemic clamp, increased significantly by 25% in both groups. Total glucose disposal during the euglycemic clamp increased from 3.51 ± 0.04 milligrams of glucose per kilogram of fat-free mass per minute (mg/kg-FFM/min) to 4.45 ± 0.54 mg/kg-FFM/min (P < 0.05) in the DPT group, but no change occurred in the D group (NS between groups). Separation of total glucose disposal rates into CHO oxidative and nonoxidative rates using indirect calorimetry during the euglycemic clamp showed that the mean CHO oxidation rate increased in the D group (P < 0.05), but not in the DPT group (NS between groups). There was, however, a significant difference in the mean CHO nonoxidative rate between the two groups (P < 0.05), increasing in the DPT group but decreasing in the D group.

In both groups, the improvements in fasting plasma glucose and meal tolerance appeared to be attributable mostly to decreased BEGP, with increased hepatic sensitivity to insulin. However, glucose disposal was accomplished by different mechanisms in the two groups.

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