Television watching from adolescence to adulthood and its association with BMI, waist circumference, waist-to-hip ratio and obesity: a longitudinal study

OBJECTIVE: To examine the prospective association of television (TV) watching from adolescence to young adulthood with BMI, waist circumference (WC), waist-to-hip ratio (WHR) and obesity. DESIGN: A community-based longitudinal cohort study. SETTING: Mater-University of Queensland Study of Pregnancy (MUSP) Cohort, Brisbane, Australia. SUBJECTS: A sub-sample of 2439 children was followed up at ages 14 years and 21 years as part of a population-based birth cohort. Offspring reported the number of TV viewing hours each day at 14 and 21 years. BMI, WC and WHR were measured at 21 years. RESULTS: In the adjusted model, offspring who watched TV for <3 h/d at 14 years but for ≥ 3 h/d at 21 years, or who watched TV for ≥ 3 h/d at 14 and 21 years, had greater BMI, WC and WHR at 21 years. Offspring who watched TV for ≥ 3 h/d at 14 years but for <3 h/d at 21 years had similar mean BMI, WC and WHR at 21 years to those who watched TV for <3 h/d at 14 and 21 years. Those offspring who reduced their TV watching hours to <3 h/d during the transition from adolescence into young adulthood were at less risk of becoming obese and those who continued or increased their TV watching to ≥ 3 h/d were at greater risk of becoming obese. This association remained independent of the potential confounding factors considered. CONCLUSIONS: The present findings suggest that our efforts to decrease obesity by reducing TV watching hours among adults should consider interventions to reduce TV time among adolescents.