The purpose of this study was to examine whether the association between daily light-intensity physical activity (LPA) and total body fat mass changes during childhood. The study sample was 577 children participating in the longitudinal Iowa Bone Development Study. Body fat mass and physical activity (PA) were measured using dual energy X-ray absorptiometry (DXA) and accelerometers, respectively, at approximately 5, 8, and 11 years of age. Age- and gender-specific multivariable linear regression models were fit to predict fat mass by LPA, adjusted for actual age, birth weight, fat-free mass, height, moderate- to vigorous-intensity PA, and physical maturity (only for girls). Among boys, LPA was negatively associated with fat mass at age 11, but not age 5 or 8. Among girls, LPA was negatively associated with fat mass at ages 8 and 11, but not at age 5. LPA may have a beneficial effect against excess adiposity among older children.
Kwon is with the Dept. of Health Studies, University of Chicago, Chicago, IL. Janz is with the Dept. of Health and Human Physiology and Dept. of Epidemiology, University of Iowa, Iowa City, IA. Burns is with the Dept. of Epidemiology and Dept. of Pediatrics, University of Iowa, Iowa City, IA. Levy is with the Dept. of Preventive and Community Dentistry, and Dept. of Epidemiology, University of Iowa, Iowa City, IA.