Replacing school and out-of-school sedentary behaviors with physical activity and its associations with adiposity in children and adolescents: a compositional isotemporal substitution analysis

Abstract

Background

Little is known on how context-specific sedentary behaviors (SB) affect adiposity. This study aimed to investigate compositional associations between context-specific SB and adiposity and estimate the differences in adiposity associated with replacing school and out-of-school SB with physical activity (PA).

Methods

This study included 336 children and adolescents. Time spent in SB and PA was estimated using multi-day 24-hour raw accelerometer data. SB and PA were specified for school and out-of-school times. Fat mass percentage (FM%) and fat mass index (FMI) were used as adiposity indicators. A compositional isotemporal substitution model was used to estimate differences in adiposity associated with one-to-one reallocations of time from context-specific SB to PA.

Results

Participants spent approximately two thirds of their school and out-of-school time being sedentary. Relative to the remaining 24-h movement behaviors, significant associations between out-of-school SB and adiposity were found in both boys ( β _ilr1 = 0.63, 95% confidence interval [CI] = 0.03–1.22 for FM%; β _ilr1 = 0.76, 95% CI = 0.03–1.49 for FMI) and girls ( β _ilr1 = 0.62, 95% CI = 0.25–0.98 for FM%; β _ilr1 = 0.80, 95% CI = 0.28–1.32 for FMI). Replacing 30 min/day of out-of-school SB with out-of-school light PA decreased FM% by 10.1% (95% CI = 3.3–17.9) and FMI by 14% (95% CI = 2.7–24) in girls. No significant associations were found for school SB.

Conclusions

A reduction of out-of-school SB in favor of light PA should be advocated as an appropriate target for interventions and strategies to prevent childhood obesity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-021-00932-6.