For years people have lived by the maxim, 'you are what you eat.' The general principle is to eat food that is good for your body. If you eat unhealthy food then you'll be unhealthy. This is good, simple advice. But it's focused on personal diet and personal health. If we wish to create more sustainable food systems then our food choices must reflect more than personal health. The challenge of creating sustainable food systems lies not in personal health but in social health, which is the essence of a sustainable society. Thousands of years ago agriculture was a pre-condition of civilization. Today, changing agriculture is a pre-condition for changing society. It is in this sense that society is what society eats. In other words, 'we are what we eat.' As the range of articles in this issue of Environments illustrate, food and society are inseparable. The choices we make about what food we eat affects every aspect of our lives. At a personal level our food choices affect our health. At a family level food choices affect how much time we spend preparing and sharing meals. At a city level they affect how we design the spaces we occupy, including where food is grown, processed, transported, purchased, and consumed. At a societal level food choices affect how many resources are required to produce food, including human resources, water, and fossil fuels. Ultimately, food defines the relations not only between personal health and personal diet but also the relations people have with their neighbours, their immediate environment, and the planet as a whole.