What is the role of government policies in encouraging healthier food choices to fight the current overweight and obesity epidemics? This report briefly examines the evidence base on unhealthy diets, including the associated burden on health systems. It then takes stock of current knowledge on the effectiveness of policy instruments to tackle unhealthy diets and proposes a four-track policy approach to encourage healthier food choices that is consistent with wider objectives for the food and agriculture sector. This policy approach includes demand side public interventions, voluntary collaboration with the food industry at the supply-demand interface, firmer regulations when public-private incentives are misaligned, and fiscal measures. This report underscores the importance of a robust evidence base for developing effective policies, which in turn requires investments in effective data systems. The Annex takes stock of how well developed food data systems are currently across a range of OECD countries and provides some recommendations on how to move forward.