title: Mediators of change in screen-time in a school-based intervention for adolescent boys: findings from the ATLAS cluster randomized controlled trial.
abstract: The mechanisms of behavior change in youth screen-time interventions are poorly understood. Participants were 361 adolescent boys (12-14 years) participating in the ATLAS obesity prevention trial, evaluated in 14 schools in low-income areas of New South Wales, Australia. Recreational screen-time was assessed at baseline, 8- and 18-months, whereas potential mediators (i.e., motivation to limit screen-time and parental rules) were assessed at baseline, 4- and 18-months. Multi-level mediation analyses followed the intention-to-treat principle and were conducted using a product-of-coefficients test. The intervention had a significant impact on screen-time at both time-points, and on autonomous motivation at 18-months. Changes in autonomous motivation partially mediated the effect on screen-time at 18-months in single and multi-mediator models [AB (95% CI) = -5.49 (-12.13, -.70)]. Enhancing autonomous motivation may be effective for limiting screen-time among adolescent males.
  
  
  BACKGROUND
  Australian New Zealand Clinical Trials Registry No: ACTRN12612000978864.
authors.affiliation: Priority Research Centre for Physical Activity and Nutrition, School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan, NSW, 2308, Australia. jordan.smith@newcastle.edu.au.
authors.forename: Jordan J
authors.initials: JJ
authors.lastname: Smith
authors.affiliation: Priority Research Centre for Physical Activity and Nutrition, School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan, NSW, 2308, Australia.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Morgan
authors.affiliation: Institute for Positive Psychology and Education, Faculty of Health Sciences, Australian Catholic University, Strathfield, NSW, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Lonsdale
authors.affiliation: Priority Research Centre for Physical Activity and Nutrition, School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan, NSW, 2308, Australia.
authors.forename: Kerry
authors.initials: K
authors.lastname: Dally
authors.affiliation: Priority Research Centre for Physical Activity and Nutrition, School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan, NSW, 2308, Australia.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Plotnikoff
authors.affiliation: Priority Research Centre for Physical Activity and Nutrition, School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan, NSW, 2308, Australia.
authors.forename: David R
authors.initials: DR
authors.lastname: Lubans
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D002648:Child; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008297:Male; D009042:Motivation; D009043:Motor Activity; D009765:Obesity / Q000517:prevention & control*; D016487:Parenting; D011203:Poverty; D057185:Sedentary Behavior
keywords: Obesity prevention; Physical activity; Rules; Sedentary behavior; Self-determination theory