The way we design our cities influences people’s physical activity and nutrition behaviours, which in turn affects chronic disease. Obesity is one of the most significant health burdens we face as a country, but very little has changed over the last 20 years. People must live in an environment that is conducive to healthy decisions to maximise the possibility of widespread and long-term behaviour change. This research will combine geographic datasets with New Zealand Health Survey data (n = 18,000 participants) to show how the built environment affects both physical activity and nutrition behaviours, and how these behaviours help to explain the link between the environment and obesity. A novel modelling tool will be produced that can predict how future urban planning decisions will affect the behaviour and health of communities.