Study Links Obesity, Urban Sprawl

In a study recently published in the Journal of Regional Science,researchers from Oregon State University found that the relationshipbetween obesity and urban sprawl may be a two-way street.

Economists Andrew Plantinga from OSU's Department of Agricultural andResource Economics and Stephanie Bernell from OSU's Department ofPublic Health expanded previous studies that showed that people livingin areas of urban sprawl tend to have higher body mass indices. Theiranalysis suggests that the relationship between obesity and urbansprawl may be due to personal preferences when choosing a home locationrather than to direct impacts of the suburban environment on physicalactivity and weight.

Location, location, location. Research by Plantinga and Bernellsuggests that an individual's body weight is a factor determining thedesirability of a residential location. They found the relationshipbetween obesity and urban sprawl can be explained by the way peoplesort themselves by personal preference.

In a follow-up study, Plantinga and Bernell used a national data set totest whether body mass index influences the decisions of adults tolocate in counties with a high or low degree of sprawl. To measure bodyweight, the researchers used data from the U.S. Department of Labor'sNational Longitudinal Survey of Youth, which has tracked statistics onthousands of individuals since their youth in 1979. The researchersexamined many factors, among them ethnicity, gender, age, income,education, marital status and body weight.

"Among people who moved recently, we find that in addition to a highbody mass index, being female, younger, and married increases theprobability of choosing to reside in a sprawling county," Bernell said.

"In many sprawling areas, distances are too great for people to walk towork or to the store," Plantinga explained. "Transportationinfrastructure is often designed for automobiles, with the result thatwalking and bicycling are impractical and unsafe. The incentives arefor people to drive instead of walk. In contrast, in urbanneighborhoods like the Pearl District in Portland, Ore., people canwalk to work, school, or shopping. In many cases, it's easier to walkto the store than to drive."

Previous studies had suggested that the relationship between obesityand urban sprawl is related to suburban environments that discourageroutine physical activity such as walking and biking. However, previousstudies did not consider the choices people make in selecting where tolive.

"When you select a residential location, you are really choosing abundle of attributes," Plantinga said. "The house you choose may benear a shopping center or a park, or it may have a three-car garage anda bonus room. The market prices each of these attributes. It followsthat individuals, given their income, will choose locations thatprovide the attributes of greatest value to them. People who valuewalking will tend to choose walkable neighborhoods. People who do notcare for walking will tend not to."

These findings have implications for urban planners and public healthofficials, according to Plantinga. Many recent planning initiativesinclude funding for bicycle and pedestrian facilities in order toincrease physical activity. However, making communities moreexercise-friendly may simply attract people who are predisposed tophysical activity.

Plantinga and Bernell's follow-up study, "The Association Between UrbanSprawl and Obesity: Is it a Two-way Street?" is available online onBernell's homepage: http://www.hhs.oregonstate.edu/faculty-staff/userinfo.php?id=22