Purpose: Physical inactivity is deleterious to health, but it has been difficult to determine the extent to which these effects are attributable to abnormal body composition or to factors related to physical activity alone. To begin to gauge independent effects of physical activity on health risk, we matched by BMI two groups of normal-weight adolescent females, one physically active (all participants in high school sports), and one sedentary.
Methods: Thirty-seven sedentary and 37 physically active adolescent females (mean 15.5 yr) were matched for age and BMI percentile (mean = 58.8). Comparisons included fitness, body composition and bone mineralization (by DEXA), circulating inflammatory cytokines, growth factors, bone-turnover markers, leptin, and adiponectin.
Results: Compared with the normal-weight sedentary girls, active girls had significantly (P < 0.05) higher fitness level (peak VO2 35.5 +/- 5.2 vs 24.4 +/- 4.1 mL.kg(-1).min(-1)), lean body mass (43.2 +/- 4.4 vs 38.7 +/- 3.6 kg), bone mineralization (spinal BMD z-scores 0.04 +/- 0.88 vs -0.41 +/- 0.85), and lower percent body fat (25.4 +/- 04.6 vs 29.7 +/- 03.7%). Additionally, active girls had lower inflammatory cytokines levels (e.g., TNF-alpha 1.7 +/- 1.3 vs 2.6 +/- 2.2 pg.mL(-1)), and leptin (17.4 +/- 11.2 vs 24.7 +/- 14.7 ng.mL(-1)), and higher bone-turnover markers (e.g. osteocalcin 12.6 +/- 7.6 vs 7.8 +/- 3.0 U.L(-1)), IGFBP-3 (6416 +/- 21280 vs 4247 +/- 1082 ng.mL(-1)), and adiponectin levels (11919 +/- 3935 vs 9305 +/- 2843 ng.mL(-1)).
Conclusion: The normal-weight, physically active group was fitter and had greater lean body mass, stronger bones, and lower levels of inflammatory markers than did the normal-weight, sedentary group. In adolescent girls, the choice of a lifestyle involving high school sports is characterized by a circulating mediator and body composition pattern that, if sustained, is associated with generally lower long-term risk of cardiovascular disease and osteoporosis.