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Targeting childhood obesity through a school-based physical activity intervention : Action Schools! BC Kravetsky, Laura Beth

Abstract

Introduction: Overweight and obesity, conditions defined by an excess amount of fat mass, have become increasingly prevalent in children. As a result, they represent serious medical, financial and social burdens for society. Low levels of physical activity (PA) are believed to be partially responsible for fueling this dramatic increase in excess body fat. School-based physical activity interventions offer a novel solution to this problem as children spend the greatest portion of their day in school. Furthermore, these interventions provide an opportunity to reach children from diverse socioeconomic and ethnic backgrounds. Objective: The primary aim of this study was to determine if Action Schools! BC, a school-based physical activity model, could positively affect change in percent (%) body fat in elementary school (Grades 4-6) children. The secondary objective was to determine if Action Schools! BC could have a positive effect on change in % body fat in children considered overweight or obese at baseline. Methods: This was a 29-month randomized controlled trial. Students were randomized by school to the intervention (INT, 7 schools, n=235) or control (CONT, 3 schools, n=111 ) condition. The AS! BC model was a school-based model specifically designed to deliver 150 minutes of physical activity per week through physical education class and classroom-based activities. Percent fat was measured using Dual-energy X-ray Absorptiometry. Group means were compared for age, race, body composition (height, weight, BMI, fat mass, % fat, lean mass, % lean) and lifestyle variables (general physical activity score (1-5), min / day of physical activity). Differences in maturity status and number of menarcheal girls were also evaluated. Physical activity delivered in schools (minutes/week) was assessed using activity logs filled out by teachers. Students with greater than or equal to 33% body fat at baseline (n=73) were considered overweight or obese and included in a subgroup analysis. Sex-specific multi-level models were used to compare change in percent fat between INT and CONT groups. Covariates included baseline % fat and change in height. In the secondary analysis, change in menarcheal status was also added to the model. Results: At baseline, students were 10.2 (± 0.6) years and INT and CONT groups were of similar racial background (>50% Asian, 30-40% Caucasian, 10-15% Other ethnicities). Students were mainly pre-pubertal (53% Tanner 1) although girls tended to be mature than boys. Teachers delivered an average of 152 minutes/week of physical activity (adjusted for school) in the INT schools compared with 94 minutes/week in CONT schools. After adjusting for covariates, girls in the INT group lost slightly less % body fat (-0.9%) compared with girls in the CONT group (-1.0%) (95% CI: -1.0-1.2). Boys in the INT group lost slightly more % body fat (-1.9%) compared with boys in the CONT group (-1.8%) (95% CI: -1.7-1.5). In the subgroup analysis, INT girls lost more % body fat than CONT girls (-3.6% vs. -3.0%, 95% CI: -3.8 to 2.7) and INT boys lost more % body fat than CONT boys (-3.5% vs. -2.3%, 95% CI: -4.5-2.2). Conclusions: Action Schools! BC was a feasible, school-based model that led to an increased delivery of physical activity opportunities in schools. However, a greater dose of physical activity over a longer timeframe may be required to win the fight against childhood obesity.

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