Abstract
BACKGROUND: Individuals born at low or high birth weight (BW) have elevated adiposity. The extent to which physical activity can mitigate this risk is unknown. OBJECTIVES: The aim of this study was to determine if associations between BW and adiposity vary by self-reported moderate-to-vigorous physical activity (MVPA) among adolescents. METHODS: We used data on adolescents in the National Health and Nutrition Examination Survey (1999-2006; 12-15 years; n = 4064). Using gender-stratified linear regression, we modelled body mass index (BMI) and waist circumference (WC) z-scores as a function of low, normal and high BW, MVPA (weekly Metabolic Equivalent of Task hours) and MVPA*BW cross-product terms, adjusting for sociodemographics, diet and, in WC models, BMI. RESULTS: Among girls with low MVPA, those born with high BW had greater BMI than normal BW; this difference diminished with greater MVPA (coefficient [95% confidence interval]: low MVPA: 0.72 [0.29, 1.14]; high MVPA: -0.04 [-0.48, 0.39]; P for interaction = 0.05). Among boys, MVPA did not modify the associations between BW and BMI. WC was unrelated to BW, regardless of MVPA. CONCLUSIONS: Findings suggest that effects of high BW in total adiposity can be more easily modified with MVPA in adolescent girls than in boys.