Prospective Associations Between Physical Activity And Fat Mass In Children Aged 11-13 Years: The Avon Longitudinal Study Of Parents And Children

Abstract

Childhood obesity is an important public health problem. Cross-sectional studies have suggested an inverse, dose-response relationship between levels of physical activity and risk of obesity in children. PURPOSE: The aim of this study was to investigate prospective associations of physical activity (measured by accelerometer) with subsequent fat mass (measured by Dual Emission X-ray Absorptiometry) in children through ages 11-13 years. METHODS: We used prospective data from a large birth cohort study - the Avon Longitudinal Study of Parents and Children. At age 11, 11,952 children were invited to participate of whom 7,159 accepted. From this group, 4,576 children (2,172 boys and 2,404 girls) were measured again at age 13 and contributed valid data on relevant variables. Our primary hypothesis was that physical activity at age 11 would predict fat mass at age 13. Gender-specific trivariate multilevel model analyses were conducted. RESULTS: Prospective associations of fat mass at age 13 (outcome) with physical activity at age 11 were strong for both total activity (accelerometer counts/min) and for min/day of moderate and vigorous physical activity (MVPA). Fifteen minutes additional MVPA per day at age 11 was associated with 9% (95% CI: 6%-11%) lower fat mass in boys and 6% (95% CI: 3%-9%) in girls at age 13. An increase of 15 min/day of MVPA through ages 11-13 was associated with a 3% (95% CI: 1%-4%) lower fat mass in boys and 3% (95% CI: 2%-4%) in girls over that period. CONCLUSIONS: Higher levels of physical activity, especially MVPA, are prospectively associated with lower levels of fat mass in early adolescent children, although with only two measures it is difficult to ascertain direction of causality. Public health interventions to raise levels of physical activity in children will be important in the fight against obesity. Supported by NIH Grant R01 HL071248-01A1