Effect of resistance exercise (body building) training on serum leptin levels in young men. Implications for relationship between body mass index and serum leptin

Available data about the influence of exercise on leptin level are controversial, and there are no studies concerning leptin levels in trained men with low fat mass plus large increase of muscle. 65 healthy young male matched for age were separated in three groups. 1) 25 non-professional body builders; 2) 21 mild overweight sedentary subjects; 3) 19 normal weight sedentary controls. Body composition was determined by bioelectrical impedance. Serum leptin was measured in duplicate by RIA. Statistics: Student’s t and Pearson’s test. Athletes showed similar BMI than overweight subjects: 26.98±0.49 vs 27.12±0.41 but lower fat mass: 12.53±0.96 vs 16.16±1.01% (p=0.0064) and lower leptin: 4.66±0.51 vs 7.31±0.76 μg/l (p=0.014). Athletes showed higher BMI than controls: 26.98±0.49 vs 23.08±0.30 (p<0.0001) but similar fat mass: 12.53±0.96 vs 12.48±0.73% and leptin: 4.66±0.51 vs 4.79+0.58 μg/l. Overweight subjects showed higher BMI than controls: 27.12±0.41 vs 23.08±0.30 (p<0.0001), higher fat mass: 16.16±1.01 vs 12.48±0.73% (p=0.0064) and higher leptin: 7.31±0.76 vs 4.79±0.589 μg/l (p=0.014). When leptin was calculated by fat mass no differences were observed between the three groups. There was a significant correlation between leptin and fat mass in all groups. Leptin correlated with BMI in overweight subjects (r=0.438, p=0.0463), but this correlation was not observed either in athletes or in controls. In conclusion 1) regardless of the high BMI characteristic of body builders, no correlation was observed with leptin; 2) trained state induced by resistance exercise does not influence leptin production independently of variations in body composition.