Significant deviation from normal weight (obesity and underweight) and lack of physical exercise have been identified as three of the most significant global behavioural risks to health. Body mass index (BMI) and levels of physical activity were measured in a sample of 1542 adults with intellectual disabilities (ID) receiving supported accommodation in nine geographical localities in Northern England. Comparative population data were extracted from the Health Survey for England 1998 and 2001. Men and women with ID living in supported accommodation are at increased risk of being significantly underweight and physically inactive. Women with ID living in supported accommodation are at increased risk of obesity. Within the population of people with ID living in supported accommodation increased behavioural health risks are associated with gender, severity of ID, age and location. Significant deviation from normal weight and lack of physical exercise are significant behavioural risks to health among people with ID.