This research will provide evidence to assist decision making and cost-effective investment in population-based public health interventions designed to prevent obesity and obesity-related health problems. We will identify and assess evidence relating to obesity-prevention interventions and provide an economic comparison of the costs and benefits associated with selected interventions appropriate for the New Zealand environment. Researchers will work with the funders of this research and with a stakeholder reference group. They will undertake systematic literature reviews, data collection and analysis, and health-economic modelling, to rank the chosen interventions in terms of their cost-effectiveness. The findings will inform policy makers about the relative merits of different investments, with a view to reducing the prevalence of a range of chronic health problems including diabetes, arthritis, cancer and obesity. This in turn will result in improved quality of life for New Zealanders and better value for money in health-care expenditure in New Zealand.