Evidence base for primary prevention of obesity in children and adolescents.

Effective interventions to prevent obesity in children have never been more necessary. There have been over 30 published reviews and meta-analyses on such interventions (randomized and controlled trials) since 2008. In summary, interventions which involve the whole community (community-based) in complex interventions (promoting healthy eating, reduction in sedentary behaviours and increase in physical activity) that target environments and upstream determinants appear to be more effective. In this article the strengths and weaknesses of community-based complex interventions which aim to prevent obesity in children will be discussed and a selection of recent and ongoing interventions that are shaping the evidence-base in this field will be highlighted (beyond those reported in other papers in this supplement: KOPS, CHILT, TigerKids, IDEFICS and TrinkFit). This paper reviews the challenges and opportunities associated with designing and evaluating community-based complex interventions and initiatives. These include a) design issues (strengths and weaknesses of different types of evidence), b) measurement of (effectiveness) outcomes, c) development of interventions (pilot work, planning frameworks and underpinning theories), d) partnership working and community engagement and e) health inequalities.