Effect of exercise intensity on glucose and insulin metabolism in obese individuals and obese NIDDM patients

OBJECTIVE - The primary purpose of this study was to evaluate the acute effect of exercise oi differing intensity on plasma glucose and insulin responses to an oral glucose challenge. RESEARCH DESIGN AND METHODS - Six obese men and six obese men with NIDDM of similar age, weight, percentage body fat, and Vo(2peak) participated in the study. Each subject underwent two 7-day exercise programs in a counterbalanced order al 2-week intervals. During each 7-day exercise period, the subjects cycled every day at a power output corresponding to 50% Vo(2peak) for 70 min or 70% Vo(2peak) for 50 min. Muscle glycogen utilization was estimated during exercise on day 7 using a [H-3]glucose infusion technique in conjunction with indirect calorimetry. During the day before and after each 7-day exercise period, a 3-h oral glucose tolerance test (OGTT) was administered after a 12-h overnight fast. RESULTS - The average caloric expenditure did not differ between exercise at 50 and 70% Vo(2peak) in both obese and obese NIDDM subjects. However, the carbohydrate oxidation was higher (P < 0.05) during exercise at 70 than 50% Vo(2peak) in obese subjects (77 +/- 5 vs. 68 +/- 6 g) and obese NIDDM subjects (70 +/- 4 vs. 58 +/- 6 g Muscle glycogen utilization was also higher (P < 0.05)during exercise at 70 than 50% Vo(2peak) in obese subjects (59 +/- 9 vs. 30 +/- 7 g) and in obese NIDDM subjects (48 +/- 5 vs. 24 +/- 5 g). In obese subjects,plasma glucose response area during the OGTT did not change after 7 days oi exercise at either 50 or 70% Vo(2peak). Plasma insulin response area during the OGTT also did not change after 7 days oi exercise at 50% at 70% Vo(2peak) (9,644 +/- 1,783 vs. 7,538 +/- 1,522 mu U . ml(-1). 180 min(-1)). In obese NIDDM subjects, both plasma glucose and insulin response areas during the OGTT did nor decrease alter 7 days of exercise at either 50 or 70% Vo(2peak). CONCLUSIONS - it is concluded that the exercise-induced improvement in insulin sensitivity is influenced by exercise intensify in obese individuals. The improved insulin sensitivity after 7 days of exercise at 70% Vo(2peak) in obese individuals may be related to greater muscle glycogen utilization during exercise. The lack of improvement in glucose tolerance and insulin sensitivity after 7 days of exercise at either 50 or 70% Vo(2peak) in obese NIDDM patients may be due to the fact that the NIDDM patients selected in the present study were relatively hypoinsulinemic.