Influence of Sex on the Changes in Regional Fat and Skeletal Muscle Mass in Response to Exercise Training in Adolescents with Obesity

Background: We retrospectively examined the sex differences in the changes in (1) total fat, total and regional subcutaneous adipose tissue (SAT), visceral fat, and intermuscular fat and (2) total and regional skeletal muscle distribution in response to aerobic exercise (AE) or resistance exercise (RE) in adolescents with obesity. Methods: Twenty-eight boys and 27 girls with obesity (BMI 95th percentile, 12-18 years) were randomly assigned to 3-month interventions (180 minutes per week) of AE or RE. Changes in total and regional fat and skeletal muscle distribution were assessed by a whole-body magnetic resonance imaging. Results: After controlling for corresponding baseline values, age, and race, changes in body weight, BMI, BMI z-score, and waist circumference were similar between exercise groups (p>0.05) and sexes (p>0.05). There were no sex or exercise group differences in the reductions in total fat, total SAT, visceral fat, or intermuscular fat. With AE, boys had greater (p<0.05) reductions in abdominal SAT as compared with girls. With RE, boys had greater (p<0.05) increases in total, upper body, and abdominal skeletal muscle as compared with girls. Independent of exercise modality, the improvement in VO2max was greater (p<0.05) in boys than in girls. Independent of sex, the increase in muscular strength index was higher (p<0.05) in the RE vs. AE group. Conclusion: With the exception of abdominal SAT, there were no sex or exercise treatment differences in the reductions in total and regional fat. In response to RE, the increases in total and regional skeletal muscle were significantly greater in boys than in girls.