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 acut e effect of exercise oi differing intensity on plasma glucose and insu lin responses to an oral glucose challenge. RESEARCH DESIGN AND METHOD S - Six obese men and six obese men with NIDDM of similar age, weight, percentage body fat, and Vo(2peak) participated in the study. Each su bject 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 es timated during exercise on day 7 using a [H-3]glucose infusion techniq ue 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 aver age caloric expenditure did not differ between exercise at 50 and 70% Vo(2peak) in both obese and obese NIDDM subjects. However, the carbohy drate oxidation was higher (P < 0.05) during exercise at 70 than 50% V o(2peak) in obese subjects (77 +/- 5 vs. 68 +/- 6 g) and obese NIDDM s ubjects (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 sub jects (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 c hange after 7 days oi exercise at 50% at 70% Vo(2peak) (9,644 +/- 1,78 3 vs. 7,538 +/- 1,522 mu U . ml(-1). 180 min(-1)). In obese NIDDM subj ects, both plasma glucose and insulin response areas during the OGTT d id 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 in dividuals. The improved insulin sensitivity after 7 days of exercise a t 70% Vo(2peak) in obese individuals may be related to greater muscle glycogen utilization during exercise. The lack of improvement in gluco se tolerance and insulin sensitivity after 7 days of exercise at eithe r 50 or 70% Vo(2peak) in obese NIDDM patients may be due to the fact t hat the NIDDM patients selected in the present study were relatively h ypoinsulinemic.