Cross-sectional and prospective impact of reallocating sedentary time to physical activity on children's body composition

Pediatr Obes. 2017 Oct;12(5):373-379. doi: 10.1111/ijpo.12153. Epub 2016 Jun 2.

Abstract

Background: The amount of time children spend in sedentary behaviours may have adverse health effects.

Objective: To examine the substitution effects of displacing a fixed duration of sedentary time with physical activity (PA) on children's body composition.

Methods: We included 386 children (197 boys). Outcomes were body mass index, waist circumference, total body fat mass and trunk fat mass assessed by dual-energy X-ray absorptiometry. Sedentary time and PA were measured with accelerometers. Data were analysed by isotemporal analyses estimating the effect of reallocating 15 and 30 min d-1 of sedentary time into light (light physical activity), and moderate-to-vigorous (MVPA) PA on body composition.

Results: Reallocating 15 and 30 min d-1 of sedentary time into MVPA was negatively associated with body fatness in cross-sectional analyses. Prospectively, reallocating 30 min of sedentary time into 30 min of MVPA was negatively associated with waist circumference (β = -1.11, p < 0.05), trunk fat mass (β = -0.21, p < 0.05), and total body fat mass (β = -0.48, p < 0.05) at follow-up (20 months). The magnitude of associations was half in magnitude and remained significant (p < 0.05) when reallocating 15 min of sedentary time into MVPA. Reallocating sedentary time into light physical activity was not related (p > 0.05) with body fatness outcomes.

Conclusions: Substituting sedentary time with MVPA using isotemporal analysis is associated with positive effects on body composition.

Keywords: Body composition; isotemporal; physical activity; sedentary time.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Absorptiometry, Photon
  • Accelerometry
  • Adipose Tissue
  • Body Composition / physiology*
  • Body Mass Index
  • Child
  • Cross-Sectional Studies
  • Exercise*
  • Female
  • Humans
  • Male
  • Prospective Studies
  • Sedentary Behavior*
  • Waist Circumference