Objective: The purpose of this study was to determine the effect of a relatively modest session of exercise on insulin sensitivity and fatty acid uptake the next day in obese adults.
Research design and methods: Eleven sedentary obese adults (male/female: 3/8; BMI 37 ± 1 kg/m(2); peak oxygen uptake [VO2peak] 20 ± 1 mL/kg/min) completed three experimental trials. On two of these occasions, subjects exercised to expend 350 kcal in the afternoon. These two exercise trials were identical except for the exercise intensity (50% VO2peak [EX50] and 65% VO2peak [EX65]) and the duration of exercise necessary to expend 350 kcal (EX50 = ≈ 70 min; EX65 = ≈ 55 min). Subjects also completed a control trial (CON), without exercise. The next morning, we measured insulin sensitivity (hyperinsulinemic-euglycemic clamp) and whole-body fatty acid uptake (palmitate rate of disappearance from plasma [Rd]).
Results: Exercise increased insulin sensitivity the next day, but whereas the 35% improvement after EX50 compared with CON was statistically significant (P = 0.01), the 20% improvement after EX65 was not (P = 0.17). Despite nearly identical values between CON and EX65 (P = 0.88), systemic fatty acid uptake was lower after EX50 compared with EX65 (P = 0.02), but not quite significant compared with CON (P = 0.07). Importantly, the change in fatty acid uptake after exercise compared with CON was negatively correlated with the change in insulin sensitivity for all trials (r = -0.60, P = 0.003).
Conclusions: A relatively modest single session of exercise in obese adults improved insulin sensitivity the next day, and a reduction in systemic fatty acid uptake in the several hours after exercise may be important for this effect.