Monday, May 31, 2004
Study links sprawling suburbs, sprawling waistlines
By Rob Stein
The Washington Post
WASHINGTON — People who live in neighborhoods where they must drive to get anywhere are significantly more likely to be obese than those who can easily walk to their destinations, according to the first study to directly demonstrate that long-suspected link.
The study of nearly 11,000 people in the Atlanta area found that people living in highly residential areas tend to weigh significantly more than those in places where homes and businesses are close together.
The effect appeared to be largely the result of the amount of time people spend driving or walking. Each hour spent in a car was associated with a 6 percent increase in the likelihood of obesity, and each half-mile walked per day reduced those odds by nearly 5 percent, the researchers found.
"The kind of neighborhood where a person lives clearly has an effect on their health," said Lawrence Frank, an associate professor of community and regional planning at the University of British Columbia, who led the study. The findings have national implications because the neighborhoods studied are representative of those across the country, he said.
"These findings are clearly the strongest evidence to date that there's a link between the built environment and obesity," Frank said.
The findings will be published in the June issue of the American Journal of Preventive Medicine but were released yesterday in advance of a conference on obesity later this week in Williamsburg, Va.
As the number of people who are overweight and obese has reached epidemic proportions in the United States, evidence has mounted that one of the main causes might be suburban sprawl.
Such neighborhoods make walking or other kinds of exercise more difficult because they often lack sidewalks, road patterns that encourage travel on foot, or shopping areas that are accessible without cars.
Last year for the first time, researchers showed that people who live in the most sprawling counties are more likely to be overweight or obese.
The new study is the first to examine the issue on a neighborhood level and link the specific characteristics of where people live to the amount of physical activity they get and how much they weigh.
Other researchers said the findings provide strong new evidence linking sprawl to obesity.
"Where you live clearly matters," said Reid Ewing of the National Center for Smart Growth at the University of Maryland, who conducted last year's county study. "If you live in a more sprawling place ... where the automobile is the only way to get around, that seems to have this negative effect on people's health."
Skeptics questioned the relationship, saying that more-sprawling neighborhoods might simply attract less physically active people and vice versa.
"It may well be that people who are in slimmer shape are the kind of people who enjoy living in those neighborhoods and naturally gravitate to those neighborhoods," said Samuel Staley, president of The Buckeye Institute for Public Policy Solutions, a think tank in Columbus, Ohio.
"It's not at all clear if you take those people and put them into a sprawling neighborhood, that they will become fat," Staley said.
For the study, Frank and his colleagues gathered detailed information from 10,898 people in 2001 and 2002, including their heights and weights, and asked them to keep a diary for two days that recorded exactly how and where they traveled, specifically how much time they spent walking and driving.
The researchers also conducted a detailed analysis of the neighborhoods throughout the Atlanta region where the participants lived, including how densely populated they are, whether they have sidewalks, whether the street patterns are conducive to walking and whether commercial buildings are located close to housing.
The researchers divided the communities into four categories based on how residential they are, and found that the odds of being obese from one to the next increased by about 12 percent.
"Having shops and services near to where you live was the best predictor of not being obese," Frank said.
Put another way, for residents, this meant that the relative risk of being obese increased by about 35 percent between the most-mixed and least-mixed areas.
The findings held true even when the researchers took age, income and education into consideration.
People were less likely to drive and more likely to walk if they lived close to businesses, but most of the people in the study walked very little, regardless of where they lived. More than 90 percent said they did not walk at all, and the average respondent spent more than one hour per day in a car.
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