Rapid leptin decrease in immediate post-exercise recovery

OBJECTIVE Leptin concentrations in humans are known to decrease in response to fasting, The aim of this work was to investigate whether leptin levels might also be modified by exercise-induced negative energy balance. SUBJECTS Eight male runners reported in the morning from 0800 to 1200 h for (i) one resting session (sitting) and (ii) one exercise-and-rest session (2 h run and 2 h rest). MEASUREMENTS Plasma leptin, free fatty acids (FFA), glycerol, cortisol and salivary cortisol were assayed in both sessions at 1200 h. RESULTS After exercise-and-rest the leptin concentrations were lower than after rest (1.7 +/- 0.1 vs 2.5 +/- 0.2 mu g/l, P < 0.05), i.e. a mean decrease of 30.3 +/- 4.5% (range 9.5-45.8). Plasma FFA, glycerol and cortisol concentrations increased: FFA 0.78 +/- 0.08 vs 0.18 +/- 0.04 mmol/l, glycerol 0.13 +/- 0.01 vs 0.04 +/- 0.01 mmol/l, and cortisol 428 +/- 36 vs 279 +/- 27 nmol/l. A negative correlation was found between plasma FFA and leptin levels (r = -0.5, P < 0.05) and between plasma glycerol and leptin levels (r = -0.5, P < 0.05). No correlation was found between leptin and cortisol levels. CONCLUSIONS In normal subjects with low body fat, a strenuous exercise-and-rest lowers leptin levels by a mean of 30%. A role of lipolysis possibly via increased plasma free fatty acids and glycerol levels is suggested. Cortisol does not seem to be involved.