Attending After-School Physical Activity Club 2 Days a Week Attenuated an Increase in Percentage Body Fat and a Decrease in Fitness Among Adolescent Girls at Risk for Obesity

Abstract

Purpose: To evaluate the effect of a 17-week intervention, including an after-school physical activity (PA) club 3 d/wk, on moderate-to-vigorous physical activity (MVPA), body mass index (BMI) z score, percentage body fat (%BF), and cardiorespiratory fitness (CRF) among fifth to eighth grade girls having a BMI z score ≥0, and explore whether intervention outcomes varied by club attendance (1 vs 2 vs 3 d/wk).

Design: Secondary analysis of data from a group randomized controlled trial (N = 1519, 10- to 15-year-old girls: n = 753 intervention; n = 766 control).

Setting: Twenty-four Midwestern US schools (n = 12 intervention; n = 12 control).

Sample: Subsample (n = 1194 girls) from trial's intervention (n = 593 girls) and control (n = 601 girls) groups having BMI z scores ≥0.

Measures: Moderate-to-vigorous physical activity (min/h), BMI z score, %BF, and CRF (${\dot{\text{V}}\text{O}}_{\text{2max}}$: mL/kg/min) were estimated at baseline and postintervention.

Analysis: Linear mixed-effect models.

Results: Intervention group gained less %BF (B = -0.35, P = .016), and their CRF decreased less (B = 0.22, P = .010) than the control. Marginally significant findings showed girls attending the club an average of 1 d/wk had greater increases in %BF (B = 0.33, P = .087) and MVPA (B = 0.20, P = .083) and a greater decrease in CRF (B = -0.20, P = .061) than girls attending 3 d/wk. No differences occurred between girls who attended 2 versus 3 d/wk for any outcomes.

Conclusions: The intervention attenuated an increase in %BF and a decrease in CRF among girls at risk for obesity from baseline to postintervention. Offering the after-school PA club 2 d/wk may be adequate for achieving outcomes.

Keywords: attendance; body mass index; exercise; female; intervention.