Journal Issue: Childhood Obesity Volume 16 Number 1 Spring 2006
Any effort to understand or reduce obesity must consider the “built environment.” Loosely defined, the built environment consists of the neighborhoods, roads, buildings, food sources, and recreational facilities in which people live, work, are educated, eat, and play. The way the built environment is created can affect many daily decisions. Whether people walk to work or school, eat frequently at fast-food restaurants, or take their children to parks may depend in part on how neighborhoods are built. When one studies the built environment in the context of the obesity epidemic, it is important to ask three questions. First, how does the built environment affect important lifestyle decisions? Second, would changing the infrastructure alter decisionmaking? And, third, would these changes affect Americans' weight and overall health? For example, although much of America's built environment has changed over the past forty years in ways that have promoted sedentary lifestyles, it is not known whether these changes have had a direct effect on obesity rates or whether changes in the built environment will lower these rates. In this paper, we attempt to shed some light on these issues.
Built environments affect children's weight by shaping both their eating habits and their physical activity. Research into the links between the physical places where children live and children's activity levels and eating habits, it must be said, is less conclusive than research in other areas covered in this volume. In the first place, research on youth is limited, though studies of adults can provide some insights for youth. A second important limitation of virtually all existing studies is the possibility of self-selection. A study may find that people who live near parks are more active than people who do not, but it cannot confidently conclude that proximity to parks is the cause of that activity. Perhaps, instead, active people choose to live near parks. A better study design would focus on the effect of environmental changes in a neighborhood on the people living there, but so far such studies have been limited to small changes such as building trails.1 Tracking major environmental changes is extremely difficult because the changes are not under the control of investigators, and most such changes take far longer to be completed than the typical research study does. The “ideal” study, the randomized trial, is simply not possible because people cannot be randomly assigned to live in particular neighborhoods.
Despite the limits of research in this area, leaders in public health have stressed the need for changes in the built environment to improve health.2 New reports by two authoritative panels recognize that consistent links between environmental factors and physical activity provide valuable evidence that should inform policy change.3 Both available evidence and common sense support four obesity- related goals: ensuring that all children have access to safe and convenient places to be physically active, ensuring that the bulk of food available to children in most settings meets nutritional guidelines, reducing promotion of unhealthful food and sedentary behaviors, and making it easy to identify and affordable to buy healthful foods.