Overweight and obesity have reached epidemic proportions in many countries, including Canada. In addition to becoming critical public health challenges in and of themselves, they represent major risk factors for chronic disease and disability (e.g. cardiovascular disease, diabetes). The various symptoms and co-morbidities associated with these chronic conditions place tremendous stress on the Canadian health care system, generating economic concern. This research takes a population health approach to the study of obesity, examining the complex relationships between individual demographics and behaviours, and aspects of the local social and physical environments. A subset of a nationally representative survey was linked to neighbourhood-level data from the 1991 Canadian Census, and analysed from a multilevel perspective. This study found substantial area-level variation in body mass index and waist circumference, and discovered an important role for neighbourhood-level characteristics independent of individual-level characteristics. These findings provide evidence that the underlying mechanisms driving the increasing prevalence of overweight and obesity may be so called obesogenic environments that encourage physical inactivity and unhealthy eating. An effective policy response must address environmental conditions in order to curb current obesity trends.