BMI AFFECTS THE LEPTIN RESPONSE TO EXERCISE TRAINING

Abstract

Serum leptin and insulin levels are higher in obese (OB) than normal weight (NW) individuals. Moreover, leptin and insulin may affect lipid and glucose metabolism through a bi-directional feedback loop. Exercise training (ET) reduces insulin levels and improves insulin sensitivity in overweight (OW) and OB individuals; however, the effect on leptin remains ambiguous. It is therefore conceivable that the initial level of adiposity may alter the leptin response to ET. PURPOSE To examine the effects of BMI on the leptin response to ET. METHODS 119 sedentary individuals exercised 4d/wk for 50 min at 60–85% HRmax for six months. For statistical analysis, individuals were categorized according to BMI: NW (BMI ≤ 25, n = 39), OW (BMI = 25.1–29.9, n = 43), and OB (BMI ≥ 30, n = 37). RESULTS At baseline, OB had higher leptin (OB 19.1 ± 13.0 vs. OW 14.8 ± 13.8 and NW 7.9 ± 6.8ng/ml, p < 0.05), insulin (OB 11.2 ± 14.3 vs. NW 5.2 ± 2.9μU/ml, p < 0.05) and %fat (OB 27.5 ± 5.3 vs. OW 22.1 ± 5.2 and NW 19.0 ± 4.8%, p < 0.05). After ET, VO2max increased in all groups (NW 34.8 ± 7.7 vs. 38.0 ± 7.8, OW 32.8 ± 7.4 vs. 36.1 ± 9.6, OB 27.9 ± 6.7 vs. 31.1 ± 7.6 ml/kg/min, p < 0.05). The NW decreased %fat (19.0 ± 4.8 vs. 17.6 ± 4.1%, p < 0.05). The OW decreased leptin by 23.7% (14.8 ± 13.8 vs. 11.3 ± 8.5 ng/ml, p < 0.05) and body weight (BW) by 1.3kg (80.2 ± 9.2 vs. 78.9 ± 8.6 kg, p < 0.05) from baseline. The OB decreased insulin by 32% (11.2 ± 14.3 vs. 7.6 ± 4.2μU/ml, p < 0.05), %fat (27.5 ± 5.3 vs. 26.4 ± 4.6%, p < 0.05), and BW by 2.0kg (99.3 ± 14.3 vs. 97.3 ± 13.3kg, p < 0.05) from baseline, while leptin was unchanged (20.9 ± 13.5 vs. 21.0 ± 16.8 ng/ml). CONCLUSIONS Six months of ET significantly reduced BW in both the OW and OB groups, but only the OW significantly decreased leptin. This suggests that, at least in the OB state, factors other than adiposity may have influenced the leptin response to ET. The decrease in insulin observed in the OB may have altered the bi-directional feedback loop, opposing the expected reduction in leptin due to exercise induced weight loss.