Effects of Adiposity on Physical Activity in Childhood: Iowa Bone Development Study

KWON, S., K. F. JANZ, T. L. BURNS, and S. M. LEVY. Effects of Adiposity on Physical Activity in Childhood: Iowa Bone Development Study. Med. Sci. Sports Exerc., Vol. 43, No. 3, pp. 443-448, 2011. Purpose: The aim of this study was to examine whether adiposity level is associated with subsequent physical activity (PA) level in childhood. Methods: Study participants were 326 children participating in the Iowa Bone Development Study. PA and fat mass were measured using accelerometers and dual-energy x-ray absorptiometry (DXA) at approximately 5, 8, and 11 yr. Data for relevant variables such as parents' education and PA levels and family income were also collected. Gender-specific generalized linear models were fit to examine the association between percentage body fat (%BF) at age 8 and intensity-weighted moderate-to vigorous-intensity PA (IW-MVPA) at age 11. Results: After adjusting for IW-MVPA at age 8, the interval between the age 8 and 11 examinations, residualized change scores of %BF and IW-MVPA from age 5 to 8, and mother's education level, %BF at age 8 was negatively associated with IW-MVPA at age 11 among boys (P < 0.05). After adjusting for IW-MVPA at age 8, physical maturity, and family income, %BF at age 8 was negatively associated with IW-MVPA at age 11 among girls (P G 0.05). Categorical data analysis also showed that the odds ratio (OR) of being in the lowest quartile relative to the highest quartile of IW-MVPA at age 11 for boys and girls with high %BF at age 8 were approximately four times higher than the OR for those with low % BF at age 8 (OR = 4.38, 95% CI = 1.05-18.24 for boys; OR = 4.48, 95% CI = 1.35-14.85 for girls). Conclusions: This study suggests that adiposity level may be a determinant of PA behavior. Specific intervention strategies for overweight children may be needed to promote PA.