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.

A well-resourced, comprehensive, population-based set of strategies is needed to attenuate and eventually reverse the current trends of increasing obesity prevalence now apparent in most countries. The Epidemiological Triad (host, vector, environment) has proven to be a robust model for other epidemics and is applied to obesity. Host-based strategies are primarily educational and these tend to be most effective among people with higher incomes and higher educational attainment. The main vectors for a high-energy intake are energy-dense foods and drinks and large portion sizes and, for low energy expenditure, machines that promote physical inactivity. Vector-based strategies that alter food formulation can have a significant impact, particularly through influencing common, high-volume foods.

The increasingly 'obesogenic' environments are probably the main driving forces for the obesity epidemic. There are many environmental strategies that can influence the physical, economic, policy or socio-cultural environments, but the evidence base for these potentially powerful interventions is small. Children should be the priority population for interventions, and improving the general socio-economic conditions for disadvantaged, marginalized or poor population sectors is also a central strategy for obesity prevention. The key settings for interventions are schools, homes, neighbourhoods, primary health care services and communities. The key macroenvironments for interventions are the transport and infrastructure sector, the media and the food sector.