Sex as a moderator of body composition following a randomized controlled lifestyle intervention among Latino youth with obesity

Background: Body composition differences between males and females emerge during adolescence and continue throughout adulthood; however, whether sex moderates body composition changes in adolescents with obesity after an intervention is unknown.

Objective: To examine sex as a moderator of changes in adiposity following lifestyle intervention.

Methods: A total of 136 Latino youth with obesity (BMI% 98.2 ± 1.3) aged 14 to 16 years old were randomized to either a 12-week lifestyle intervention (27 males/40 females) or control (35 males/34 females) group. The intervention included nutrition education (1 h/wk) and moderate-to-vigorous physical activity (3 h/wk). Anthropometric data (body mass index [BMI], BMI%, waist circumference, total body fat, and fat-free mass) were obtained pre- and post-intervention. Sex differences were examined by general linear models with significance determined at P < .05 for the F-statistic.

Results: Sex did not moderate changes in BMI (F_1,115 = 0.01, P = .9), BMI% (F_1,115 = 0.14, P = .7), or waist circumference (F_1,117 = 1.1, P = .3). Sex significantly moderated changes in body fat percent (F_1,117 = 5.3, P = .02), fat mass (F_1,116 = 4.5, P = .04), and fat-free mass (F_1,116 = 4.3, P = .04). Intervention males compared with females had greater relative reductions in fat percent (-4.1 ± 0.8% vs -1.2 ± 0.7%, P = .02) and fat mass (-5.0 ± 1.1 kg vs -1.5 ± 0.9 kg, P = .02) and gained more fat free mass (3.6 ± 0.9 kg vs 0.5 ± 0.8 kg, P = .02) when compared with same sex controls.

Conclusion: Males and females exhibited a differential response to lifestyle intervention for percent fat, fat mass, and fat-free mass indicating that sex-specific improvements in body composition favours males over females.