Datar A, et al. - Experts sought to determine if exposure to communities with higher rates of obesity increased the body mass index (BMI) of individuals (calculated as weight in kilograms divided by height in meters squared) and their risk of being overweight or obese. They further analyzed whether social contagion, shared environments, or self-selection could account for identified differences. An association of exposure to counties with higher rates of obesity was found with higher BMI and higher odds of overweight and/or obesity in parents and children. Findings did not support self-selection or shared built environments as possible explanations, which implied the presence of social contagion in obesity.