Childhood Obesity Policy Mixes and Prevalence Trajectories in Eight OECD Countries: A Structured Comparative Analysis Using Open-Access Data

Background: Childhood obesity prevalence and policy responses vary markedly across high-income nations, yet structured cross-country comparisons using only freely available data are rare. This review asks: What combinations of prevention policies characterise OECD countries with divergent childhood obesity trajectories, and what does the published economic evidence suggest about their potential returns?

Methods: We conducted a structured comparative analysis of eight OECD countries, selected using transparent prevalence-based criteria: four with the lowest childhood overweight/obesity prevalence (ages 5–19) in 2022 (Japan, South Korea, Netherlands, Denmark) and four with the highest prevalence that have implemented at least one major national obesity prevention policy (United Kingdom, Chile, Mexico, United States). Prevalence trends (2000–2022) were extracted from the NCD Risk Factor Collaboration open database. National policy profiles were compiled from OECD Reviews of Public Health, WHO COSI reports, and peer-reviewed evaluations, and categorised across five domains (fiscal, school-based, food labelling, marketing regulation, physical activity). Published economic evaluations were identified and synthesised narratively.

Results: The four low-prevalence countries (13.5%–18.1%) shared a pattern of early, sustained investment in school-based nutrition, daily physical activity, and active-transport infrastructure, with childhood obesity rates remaining below 20% throughout. The high-prevalence group (29.3%–46.4%) introduced comprehensive regulatory packages more recently—including sugar-sweetened beverage taxes, front-of-pack warning labels, and advertising restrictions—yet their obesity rates continued to rise or plateaued only in the most recent period. The UK’s Soft Drinks Industry Levy was associated with a flattening of obesity prevalence in primary school children, though prevalence had already been stabilising in some age groups before the levy was implemented. Chile’s labelling law reduced sugary drink purchases by approximately 25% but overall prevalence continued to rise. Mexico’s SSB tax lowered consumption in lower-income households without reversing the upward prevalence trend. Published economic simulations, where available, consistently project long-term net savings from multi-component interventions, though all estimates carry substantial modelling uncertainty.

Conclusions: No single policy type differentiates low- from high-prevalence countries. Low-prevalence nations typically began preventive efforts earlier and embedded them deeply into education and urban systems over decades. The findings support a long-term, systems-wide strategy rather than reliance on any isolated measure. This synthesis demonstrates that open-access OECD and WHO data can robustly support international policy comparisons, though causal conclusions remain limited by the ecological design.

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