title: What works in school-based energy balance behaviour interventions and what does not? A systematic review of mediating mechanisms.
abstract: OBJECTIVE
  Obesity prevention requires effective interventions targeting the so-called energy balance-related behaviours (that is, physical activity, sedentary and dietary behaviours). To improve (cost-)effectiveness of these interventions, one needs to know the working mechanisms underlying behavioural change. Mediation analyses evaluates whether an intervention works via hypothesised working mechanisms. Identifying mediators can prompt intervention developers to strengthen effective intervention components and remove/adapt ineffective components. This systematic review aims to identify psychosocial and environmental mediators of energy balance-related behaviours interventions for youth.
  
  
  METHODS
  Studies were identified by a systematic search of electronic databases (PubMed, Embase, PsycINFO, ERIC and SPORTDiscus). Studies were included if they (1) were school-based randomised controlled or quasi-experimental studies; (2) targeted energy balance behaviours; (3) conducted among children and adolescents (4-18 years of age); (4) written in English; and (5) conducted mediation analyses.
  
  
  RESULTS
  A total of 24 studies were included. We found strong evidence for self-efficacy and moderate evidence for intention as mediators of physical activity interventions. Indications were found for attitude, knowledge and habit strength to be mediators of dietary behaviour interventions. The few sedentary behaviour interventions reporting on mediating effects prevented us from forming strong conclusions regarding mediators of sedentary behaviour interventions. The majority of interventions failed to significantly change hypothesised mediators because of ineffective intervention strategies, low power and/or use of insensitive measures.
  
  
  CONCLUSIONS
  Despite its importance, few studies published results of mediation analysis, and more high-quality research into relevant mediators is necessary. On the basis of the limited number of published studies, self-efficacy and intention appear to be relevant mediators for physical activity interventions. Future intervention developers are advised to provide information on the theoretical base of their intervention including the strategies applied to provide insight into which strategies are effective in changing relevant mediators. In addition, future research is advised to focus on the development, validity, reliability and sensitivity of mediator measures.
authors.affiliation: Department of Public and Occupational Health, VU University Medical Center, EMGO Institute for Health and Care Research, Amsterdam, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: van Stralen
authors.forename: M
authors.initials: M
authors.lastname: Yildirim
authors.forename: S J
authors.initials: SJ
authors.lastname: te Velde
authors.forename: J
authors.initials: J
authors.lastname: Brug
authors.forename: W
authors.initials: W
authors.lastname: van Mechelen
authors.forename: M J M
authors.initials: MJ
authors.lastname: Chinapaw
mesh_terms: D000293:Adolescent; D001521:Behavior Therapy / Q000191:economics; D002648:Child; D002675:Child, Preschool; D003362:Cost-Benefit Analysis; D004032:Diet; D002149:Energy Intake; D004734:Energy Metabolism; D005247:Feeding Behavior; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D017008:Negotiating / Q000379:methods / Q000523:psychology; D009765:Obesity / Q000191:economics / Q000517:prevention & control* / Q000523:psychology; D040242:Risk Reduction Behavior; D012574:Schools / Q000191:economics