Food choices are deeply embedded in social norms, personal values, habits and aspirations; intervening to change dietary behaviour is a difficult and controversial area. The overlap between healthy diets and sustainable diets is a useful starting point. Social norms will need to change if European diets are to become environmentally sustainable.Our behaviour is motivated by a mix of social-psychological drivers (social norms, values, attitudes, identity, habits, etc) and infrastructural drivers (prices, regulations, availability, technology, advertising, etc). Changing behaviour is notoriously challenging, and changing food habits is particularly difficult, partly because food tends to be such an emotive issue, bound up with our cultural and personal perceptions of what a ?normal? diet is. Social norms do change over time, as with attitudes to drinkdriving, or smoking; such changes in normal practices can be lead by governments, as well as being promoted by businesses and civil society.