Leptin reduction after endurance races differing in duration and energy expenditure.

Serum leptin concentrations are reduced in the presence of a negative energy balance. It has been demonstrated, however, that strenuous and prolonged exercise, which induces a marked negative energy balance, is not always followed by a reduction in serum leptin levels. We therefore analysed serum leptin concentrations before and after three endurance races, which differed in duration and energy expenditure (EE), with the aim of clarifying the relationship between the level of EE and the reduction in leptin levels.