Acute exercise effect on postabsorptive serum leptin

We postulated that high circulating cortisol levels during intense exercise would lead to increased serum leptin concentrations. Young, lean men ate a small meal and then exercised on a cycle ergometer for 41 min or rested on a control day. Serum leptin concentration was 10% greater during exercise than in the control condition (P < 0.05). Directly after exercise, serum le ptin dropped to;10% less than the control level (P, 0.05) but had recovered to the nonexercised level after <similar to>2 h of recovery. Rapid exercis e effects on circulating leptin were related to changes in hemoconcentratio n rather than changes in leptin mass. When serum leptin was normalized to s erum protein, leptin increased by 10% in the exercise condition compared wi th control by the end of recovery (P, 0.05). Although exercise increased se rum cortisol concentration threefold, there was no relation between differe nces in cortisol and exercise vs. control differences in normalized leptin. The increased leptin mass after exercise may have been related to greater plasma glucose concentration during recovery after exercise compared with t he control condition.