Associations of total sedentary time, screen time and non-screen sedentary time with adiposity and physical fitness in youth: the mediating effect of physical activity

ABSTRACT

The aims of the present study were: i) to examine the associations of total accelerometer-based sedentary time (ST) and specific-domain self-reported ST (i.e., screen-based, educational-based, social-based, and other-based ST) with adiposity and physical fitness in youth; and ii) to analyse the mediation effect of physical activity (PA) on associations.

This study was conducted with 415 children (9.1 ± 0.4 years) and 853 adolescents (13.6 ± 1.6 years) in Spain during 2011–2012. Total ST and PA were assessed by accelerometry. Leisure-time spent in twelve sedentary behaviours was self-reported. Adiposity and physical fitness was measured following the ALPHA battery for youth.

Total accelerometer-based ST was positively associated with global adiposity score in children, and negatively associated with global physical fitness score in children and adolescents; but relationships were not independent of PA. PA mediated all associations of accelerometer-based and self-reported ST with adiposity or physical fitness in children. Conversely, screen-, educational-, social-, and other-based ST were negatively related to physical fitness in adolescents, independently of PA.

These findings give an impetus to developing effective strategies for specifically promoting PA in children and for increasing PA while reducing ST in adolescents in order to produce improvements on adiposity and physical fitness.

KEYWORDS:

• Adiposity
• physical fitness
• sedentary time
• screen time
• non-screen sedentary time

Acknowledgments

The authors gratefully acknowledge the youth, parents and teachers who participated in this study. The UP&DOWN Study was supported by the DEP 2010-21662-C04-00 grant from the National Plan for Research, Development and Innovation (R + D + i) MICINN. VCS was supported by FPI grant from Autonomous University of Madrid. IEC is supported by a grant from the Alicia Koplowitz Foundation. The funding organizations had no role in the study design, the collection, analysis or interpretation of the data or the decision to submit the manuscript for publication.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the National Plan for Research, Development and Innovation (R + D + i) MICINN [DEP 2010-21662-C04-00];Post-doctoral grant (Alicia Koplowitz Foundation) [n/a];FPI grant (Autonomous University of Madrid) [n/a].