It's a long-standing question: What causes suburban sprawl? No, not the unbridled growth of exurbia but, rather, what's behind the growth of suburbanites' - well - behinds?
That's something Karen Mumford would like to know. The Atlanta academic is part of an unusual partnership between a real estate developer and public-health research team that aims to find out whether people would be more inclined to walk if there was something they could walk to.
She's hooking up study participants to high-tech pedometers and global-positioning devices to track their activity before and after they move into a development in Atlanta that promises a walk-to-nearly-everything lifestyle.
"Imagine if you could get your physical activity just by doing routine things and not having to go out and `exercise,' " said Mumford, an assistant professor at the Rollins School of Public Health at Atlanta's Emory University.
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Her study is among the latest that have looked for links between sprawl in exurbia and in the U.S. population. Some researchers estimate that in the last five years, hundreds of investigations have probed possible links between car-dependent neighborhoods and a nationwide epidemic of spare tires.
"We found no connection," said University of Toronto economics professor Matthew Turner, who last fall released a study that roiled many proponents of "smart growth." The study reported advocates reining in sprawl via denser, more land-efficient development.
Turner, however, noted that people living in sprawling neighborhoods tended to be heavier than those where shops and other amenities are within walking distance. But he attributes that to obese people being more likely to live where they can get around by car.
"People are sorting themselves," Turner said. "Sure, there's a relationship. It's that people who don't like to walk move to where they don't have to."
It's turning into the old chicken-and-egg thing.
"If my numbers are right, 18 out of 20 studies show significant links between the built environment and obesity," said Reid Ewing, an urban planner who is a professor at the National Center for Smart Growth at the University of Maryland.
Ewing said his 2003 collaborative study was the first national research to establish a direct association between sprawl - suburban developments whose only link to other places is busy roads with few sidewalks - and the health of those who live there.
The weight difference between living in sprawl and living in "walkable" communities: six pounds, he said.
"When you account for (numerous variables), the people living in the most sprawling areas are likely to weigh six pounds more than people in the most compact counties," he said.
Ewing's report coincided with a public health outcry over obesity, he said, stimulating academic interest in a sprawl-weight link. He estimates that 15 to 20 obesity-sprawl studies have been started since his report.
Siim Soot led one such effort. The director emeritus of the Urban Transportation Center at the University of Illinois at Chicago last year presented research that said fat was related less to suburban sprawl than to education.
His research calculated height and weight data from about 7 million driver's licenses and correlated them with numerous socioeconomic and housing factors in 300 ZIP codes.
Residents of higher-income areas with high percentages of college-educated residents were less likely to be obese, he said.
"We found that education was the most important variable, followed closely by income," Soot said.
Soot agreed that the topic seems to have gained academic momentum in the last five years, estimating that 100 studies have gotten under way in that time.
But Turner says even that number is far too low. He says a casual search of the terms "sprawl" and "obesity" through Google Scholar, which tracks academic research, yields more than 1,000 study titles.
It's all part of the broader international debate over smart growth, which in the last decade has found favor with urban planners and municipal officials.
Some traditional developers argue that there is more than one way to exercise, and that they are meeting consumer demand by incorporating amenities that are intended to get residents moving. Walking trails have become almost commonplace in sizeable developments, and a few developers are constructing fitness facilities and sport courts.
"If you put exercise facilities within a couple of minutes' reach, they'll definitely use them," said Mary Breedlove, facilities manager for Macom Development in Naperville, Ill.
But she concedes that the residents are reluctant to let go of their cars.
"I've seen them strap their kids into their car seats and drive across the street to the swim club," she said.
Both sides agree that the topic can be politically charged, with the potential to influence public health and land-development policies.
"There is a political agenda" among critics of smart-growth policies, Ewing said. "There are libertarian think tanks, anti-planning, pro-development groups that ... when we put out our research, they attack."
Turner is equally dismissive of those who connect sprawl to obesity. "Most of the literature is ideologically driven by people who want other people to live in townhouses," he said. "(They say) we ought to be taking some sort of action to change neighborhoods so people will lose weight, in spite of the fact that we haven't established a causation."
Researcher Mumford was mindful of the debate when she began working with real estate agents in May to recruit study participants at Atlantic Station, a 138-acre development near the heart of Atlanta that eventually will include 132,000 households and 8 million square feet of offices, retail stores and entertainment venues.
Though her $500,000 study is largely funded by the federal Centers for Disease Control, it got a supplemental grant from AIG Global Real Estate Investment Corp., developer of Atlantic Station.
Mumford said the AIG money will pay for the global-positioning systems and high-tech pedometers that will record the participants' physical activity.
In addition to diaries and interviews of study participants, the electronic data will provide objective measurements, she said.
"That way, there would be no perception that you're trying to help the development community" by bolstering the premise that a "walkable" development translates into good health, she said.
AIG executive Brian Leary said, nonetheless, that Atlantic Station hopes the study validates perceptions of healthful living in a walk-to-everything community.
Green building is a hot-button in housing, he said, and health could be the next one. "We anticipate home buyers saying, `I want the Good Housekeeping Seal of Approval for my health too,'" Leary said.
In about a month Amanda Matthews will move to an Atlantic Station condo from a suburban apartment complex about five miles away. She said she is looking forward to less car time.
"I absolutely drive everywhere now," said Matthews, 28, the first of 200 study participants. But she said the attraction of the development wasn't exercise - she works out at a gym five or six times a week - but socialization.
"I love that there are people outside, that there are restaurants and movie theaters and I can walk there," she said.
Matthews said the debate about a link between walkability and weight probably would require studies of 20 years or more to resolve.
"I think that 10 percent of people will exercise, no matter what, and 10 percent won't exercise, no matter what," Matthews said. "Maybe there's a population in the middle that will walk more because they moved someplace that would affect their level of exercise."