JUNE 2007 HOT TOPICS

Severe Obesity Is Increasing Rapidly in the United States

It is well known that obesity in the U.S. population has been increasing, and Congress is looking for ways to address the epidemic. However, new research by RAND economist Roland Sturm shows an even more disconcerting trend: Severe obesity (a body mass index higher than 40, or about 100 pounds or more overweight) is increasing twice as fast as moderate obesity. Between 2000 and 2005, the proportion of Americans who are severely obese increased by 50 percent. The explosive increase in the number of bariatric surgical procedures (including stomach reductions and gastric bypass) has made no noticeable dent in the prevalence of severe obesity. Obesity is linked to higher health care costs than are smoking or drinking, and it plays a major role in disability at all ages. While moderate obesity increases health care expenditures by about one-third, severe obesity doubles them, a consequence of early onset of common chronic conditions, such as diabetes. The cost consequences of disability among the young could swamp recent Medicare and Medicaid savings stemming from increasingly good health among the elderly.

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Neighborhoods Can Reduce the Risk of Obesity

Researchers are seeking to understand environmental factors that may contribute to obesity or help to prevent it, and Congress has recognized the importance of these factors in wellness by introducing several pieces of related legislation. A series of studies led by RAND researcher Deborah Cohen assessed the effect of neighborhoods on physical activity and weight. A study of park use in Los Angeles found that neighborhood parks promote exercise, especially among residents who live within a mile of a park. Even though many residents used parks for sitting or other sedentary activities, they got exercise by walking to the park and back. A second study found that school playgrounds may provide a valuable resource for weekend exercise. Adolescent girls who lived in cities with a higher share of accessible school playgrounds on weekends in their neighborhoods had a significantly lower body mass index than their counterparts had in cities with more locked playgrounds. A third study examined urban design features and their impact on walking. Results showed that residents took more walking trips in neighborhoods with four or more types of businesses and with more four-way intersections. A fourth study examined the effect of neighborhood social ties—known as collective efficacy—on children's weight. Collective efficacy was measured by determining whether a neighborhood contains adults who children look up to, who are willing to help, who get along with their neighbors, who take active steps to ensure that children are safe, who share the same values, who will intervene if a youngster is defacing property with graffiti, and who will scold a child showing disrespect. In neighborhoods with high collective efficacy, children were less likely to be overweight than their peers in neighborhoods with low levels. Taken together, the studies indicate that factors beyond individual control, such as neighborhood design and features, affect diet and physical activity.

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RESEARCHER PROFILES

Roland Sturm, Ph.D., is a Senior Economist at RAND. Dr. Sturm's recent research has focused on the economics of healthy living; health care costs of poor health habits; changes of mental health and substance abuse services under managed care; and effects of the parity legislation for behavioral health care. He is the author of more than 100 scientific publications, has testified on health care issues before Congress and several state legislatures, and is a past winner of the NIHCM's Award for excellence in health services research. His latest projects analyze how urban design and neighborhood characteristics affect lifestyles and health outcomes. Read more work by Dr. Roland Sturm »

Deborah Cohen, MD, MPH, is a Senior Natural Scientist at RAND with interests in how the social and physical environment influences health and health behaviors. She has led several large scale studies examining physical activity, sexually transmitted diseases, HIV and alcohol use prevention. Current projects include evaluating community-based interventions to promote physical activity and healthy eating, examining the impact of park improvements on physical activity, the association between the availability of alcohol and other foods on drinking and eating behaviors. She is the co-author of the book, “Prescription for a Healthy Nation: A new approach to improving our lives by fixing our everyday world.” Read more work by Dr. Deborah Cohen »

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