Obesity is the result of people consistently consuming more calories than they expend. A complex interaction of social and environmental conditions affects both energy consumption and physical activity levels. These conditions include, but are not limited to the following factors: the availability of affordable and healthy food; price disparities between healthy and less healthy foods; access to or perceived safety of recreation facilities; and the conduciveness of the physical environment to active modes of transportation, such as walking and biking. As (...) outlined in the “Assessing Laws and Legal Authorities for Obesity Prevention and Control” paper in this supplement issue, laws and government policies in the United States influence nearly all of these social and environmental factors. (shrink)