Obesity is a significant health and social problem which has reached pandemic levels. The obesogenicity of an environment has been defined as 'the sum of influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individuals or populations'. Prevention and treatment of obesity has focused on pharmacological, educational and behavioural interventions, with limited overall success. A novel and a longer-term approach would be to investigate the environments that promote high energy intake and sedentary behaviour; this has not yet been fully understood. The obesity epidemic has attracted attention at all levels, from general media interest to policy and practice from health and other professions including urban designers and planners. Shaping the environment to better support healthful decisions has the potential to be a key aspect of a successful obesity prevention intervention. Thus in order to develop effective environmental interventions, in relation to obesity, we need to understand how individuals, and different groups of individuals, interact with their environments in terms of physical activity and food intake.