Abstract The rapid rise in obesity rates over the last 30 years has profound implications for the health of populations. That this rise has occurred over a relatively short biological time scale suggests that changes in the environments to which we are exposed may be to blame, rather than individual genetic endowment. Focusing on developed world nations, this article briefly reviews this emerging ‘ecological’ perspective in the search for the causes of obesity. This article explores how aspects of our environment might disrupt ‘energy balance’ through influencing food consumption and physical activity. It focuses on three hypothesised pathways for environmental risk: the organisation of built physical space, the social environment and the political environment. The article demonstrates that a consideration of scale and context are also important in the search for the environmental drivers of weight gain.