In an aspirational global food system, everyone would meet but not exceed their nutritional needs, and fulfill personal preferences for tasty, affordable, varied, convenient and healthy food—while keeping climate change under 2°C. Diets are an outcome of people’s choices and are profoundly shaped by socio-cultural, physical and economic factors in the food ‘choice environment’. Historically there have been substantial changes in people’s diets and diets continue to be in flux. Dietary change offers a route to achieving the aspirational Sustainable Development Goal (SDG) food system, combining positive outcomes for health and for the environment. The most effective strategies to shift diets will involve multiple approaches that deliberately aim not just to influence consumers themselves, but all participants in the food system, taking into account plural values and incentives. Effectiveness of actions will depend on the political economy at national and global levels.