Plasma leptin and energy expenditure during prolonged, moderate intensity, treadmill exercise

Current literature shows conflicting results regarding the possible direct role of exercise on leptin concentrations, mainly because of a non-homogeneous level of energy expenditure (EE) and the lack of standardization of energy balance.

The aim of the study was to evaluate the effect of exercise duration and its corresponding EE on leptin levels, during prolonged treadmill exercise, in a well-controlled laboratory setting.

Seven young trained males underwent a 4-h treadmill exercise. The starting intensity was set at 65% of maximal oxygen consumption. At the start of the test and throughout the exercise, venous blood samples were drawn for the assays of leptin, glucose, free fatty acids (FFA), cortisol, epinephrine (E) and norepinephrine (NE). Hourly and total EE was monitored with gas analysis.

Plasma leptin levels decreased from 1.10±0.15 to 0.85±0.26 μg/l (p<0.01) at the end of the exercise, reaching a significant reduction already after the second hour. FFA and cortisol showed a progressive significant increase, while glucose did not significantly change throughout the test. Plasma E and NE significantly increased at all sampling times compared to basal values (48.1±30.3 to 352.3±187.7 pg/ml, p<0.001 and 238.1±118.9 to 1798.7±413.5 pg/ml, p<0.001). The random-effects model for panel data analysis showed negative correlation between leptin, NE and the values of progressive EE (r2=0.745, p<0.05).

Our data demonstrate that, during a prolonged moderate intensity exercise, leptin decrease is significantly related to the total EE. Further, NE concentrations seem to play an important role in the inhibition of leptin secretion.