Studies of school-based interventions designed to prevent overweight or overweight-related diseases (such as cardiovascular diseases) in children (aged five to 18 years) were eligible for inclusion in the review. Relevant interventions had to use an educational approach and contain a diet and/or physical activity aimed at producing a behavioural change. Eligible outcomes were body weight or adiposity (for example, body mass index or skin folds). Studies that did not assess a general population of children and studies that specifically focused on treating obese children with eating disorders in a clinical setting were excluded from the review.
Included interventions were multi-component programmes that included different combinations of diet and/or physical activities; two interventions also included other additional components. Where relevant, interventions were compared to a usual curriculum, no intervention or minimal intervention control. Interventions were mostly targeted at mixed gender groups of children aged from five to 12 years. One study targeted older children (teenage girls aged 14 to 17 years). Single studies targeted single-sex groups of boys and girls. The duration of intervention programmes ranged from 16 weeks to three years. Outcome measures varied between studies (further details were reported in the review). Most studies were conducted in USA and the rest in UK, Canada and Israel.
Studies were assessed by one reviewer. Where there was doubt about the eligibility of a study a second reviewer was consulted. If the two reviewers failed to reach consensus, the study was included in the review.