title: Systematic review and meta-analysis of school-based interventions to reduce body mass index.
abstract: BACKGROUND
  Childhood obesity predisposes to adult obesity and increases the risk of many diseases. Schools provide a vehicle to deliver public health interventions to all children.
  
  
  METHODS
  Medline and Embase were used to undertake a systematic review of published studies of school-based interventions aimed at reducing the body mass index (BMI) of children ≤ 18 years. Preferred reporting items for systematic reviews and meta-analyses guidelines were followed, and eligible studies subjected to a random effects meta-analysis.
  
  
  RESULTS
  Between 1991 and 2010, 43 published studies provided 60 measurements of effect. The pooled effect was a 0.17 (95% CI: 0.08, 0.26, P < 0.001) reduction in BMI. Heterogeneity was high (I(2) = 93.4%) but there was no significant small study bias (Egger's test, P = 0.422) nor significant variation by length of follow-up. The intervention comprised physical activity only in 11 (26%) studies, education only in three (7%), and combinations of these and improved nutrition in the remaining 29 (67%). On stratified analysis, physical activity used in isolation (-0.13, 95% CI: -0.22, -0.04, P = 0.001) or combined with improved nutrition (-0.17, 95% CI: -0.29, -0.06, P < 0.001) was associated with significant improvements in BMI. Interventions targeted at overweight/obese children reduced their BMI by 0.35 (95% CI: 0.12, 0.58, P = 0.003). Those delivered to all children reduced it by 0.16 (95% CI: 0.06, 0.25, P = 0.002).
  
  
  CONCLUSIONS
  There is growing evidence that school-based interventions that contain a physical activity component may be effective in helping to reduce BMI in children.
authors.affiliation: Centre for Population Health Sciences,  University of Glasgow, Glasgow G3 8YU,  UK.
authors.forename: H V
authors.initials: HV
authors.lastname: Lavelle
authors.forename: D F
authors.initials: DF
authors.lastname: Mackay
authors.forename: J P
authors.initials: JP
authors.lastname: Pell
mesh_terms: D015992:Body Mass Index; D002648:Child; D006293:Health Promotion / Q000706:statistics & numerical data*; D006801:Humans; D009765:Obesity / Q000453:epidemiology / Q000517:prevention & control*; D050177:Overweight / Q000453:epidemiology / Q000517:prevention & control; D011634:Public Health / Q000379:methods*; D012574:Schools; D013223:Statistics as Topic; D013334:Students; D014481:United States / Q000453:epidemiology