PURPOSE We investigated the influence of Leptin (LEP) and leptin receptor (LEPR) SNPs on habitual physical activity (PA) and body composition response to a unilateral, upper body resistance training (RT) program. METHODS European-derived American volunteers (men=111, women=131, 23.4±5.4 yr, 24.4±4.6 kg·m−2) were genotyped for LEP 19 G>A (rs2167270), and LEPR 326 A>G (rs1137100), 668 A>G (rs1137101), 3057 G>A (rs1805096), and 1968 G>C (rs8179183). They completed the Paffenbarger PA Questionnaire. Arm muscle and subcutaneous fat volumes were measured before and after 12wk of supervised RT with MRI. Multivariate and repeated measures ANCOVA tested differences among phenotypes by genotype and gender with age and body mass index as covariates. RESULTS Adults with the LEP 19 GG genotype reported more kcal/wk in vigorous intensity PA (1273.3±176.8, p=0.017) and sports/recreation (1922.8±226.0, p<0.04) than A allele carriers (718.0±147.2, 1328.6±188.2, respectively). Those with the LEP 19 GG genotype spent more hr/wk in light intensity PA (39.7±1.6) than A allele carriers (35.0±1.4, p=0.03). In response to RT, adults with the LEPR 668 G allele gained greater arm muscle volume (67687.05±3186.7 vs. 52321.87±5125.05 mm3, p=0.01) and subcutaneous fat volume (10599.89±3683.57 vs. −5224.73±5923.98 mm3, p=0.02) than adults with the LEPR 668 AA genotype, respectively. CONCLUSION LEP19 G>A and LEPR 668 A>G associated with habitual PA and the body composition response to RT. These LEP and LEPR SNPs are located in coding exons likely influencing LEP and LEPR function. Further investigation is needed to confirm our findings and establish mechanisms for LEP and LEPR genotype and PA and body composition associations we observed.

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