A secondary analysis of the childhood obesity prevention Cochrane Review through a wider determinants of health lens: implications for research funders, researchers, policymakers and practitioners.

BACKGROUND: Randomised controlled trials (RCTs) are often regarded as the gold standard of evidence, and subsequently go on to inform policymaking. Cochrane Reviews synthesise this type of evidence to create recommendations for practice, policy, and future research. Here, we critically appraise the RCTs included in the childhood obesity prevention Cochrane Review to understand the focus of these interventions when examined through a wider determinants of health (WDoH) lens. METHODS: We conducted a secondary analysis of the interventions included in the Cochrane Review on "Interventions for Preventing Obesity in Children", published since 1993. All 153 RCTs were independently coded by two authors against the WDoH model using an adaptive framework synthesis approach. We used aspects of the Action Mapping Tool from Public Health England to facilitate our coding and to visualise our findings against the 226 perceived causes of obesity. RESULTS: The proportion of interventions which targeted downstream (e.g. individual and family behaviours) as opposed to upstream (e.g. infrastructure, environmental, policy) determinants has not changed over time (from 1993 to 2015), with most intervention efforts (57.9%) aiming to change individual lifestyle factors via education-based approaches. Almost half of the interventions (45%) targeted two or more levels of the WDoH. Where interventions targeted some of the wider determinants, this was often achieved via upskilling teachers to deliver educational content to children. No notable difference in design or implementation was observed between interventions targeting children of varying ages (0-5 years, 6-12 years, 13-18 years). CONCLUSIONS: This study highlights that interventions, evaluated via RCTs, have persisted to focus on downstream, individualistic determinants of obesity over the last 25 years, despite the step change in our understanding of its complex aetiology. We hope that the findings from our analysis will challenge research funders, researchers, policymakers and practitioners to reflect upon, and critique, the evidence-based paradigm in which we operate, and call for a shift in focus of new evidence which better accounts for the complexity of obesity.