Obesity has many causes, but currentresearch indicates that sprawl may play a part. So far, researchers have concluded that people who live in sprawling, car-dependent neighborhoods are more likely to be obese, while people who live in walkable neighborhoods are apt to do more walking. But researchers still trying to tease out cause and effect: do walkable neighborhoods encourage people to walk? Or do people who like to walk move to walkable neighborhoods? I suspect it is both.
However, one recently study claims that sprawl doesn’t, in fact, cause obesity. The authors, who base their findings on a complex theoretical model, don’t dispute that sprawl and obesity are linked. But they claim that people who move to sprawling neighborhoods are simply making a more-or-less conscious choice to put on more weight:
"[R]esidents are willing to accept locations that result in weight gain because they face lower housing prices and can purchase more housing."
In other words, people buying a house don’t mind putting on a few extra pounds in order to get the house they want.
But here’s the catch: the link between sprawl and obesity just isn’t that widely known. Researchers have just been started exploring these connections over the last few years; the literature is growing, but it’s still in its infancy. So it’s hard to imagine that most home-buyers, over the last several decades, were weighing the concrete effects of neighborhood design on their health. How could they, when the information just didn’t exist?
While I haven’t worked through the entire model line-by-line, I also have some quibbles with the methods. As with any theoretical model, it’s based on a host of assumptions. And one of them—that calorie consumption increases as income increases—clearly poses problems. As Clark blogged about a while ago, food is really cheap, and cheapest foods are the most calorie dense (think greasy fast food). So there’s ample reason to believe that calorie consumption could actually increase as income goes down.
Theory can be very useful; and there may well be some truth to the notion that people who don’t like exercise don’t mind living in places that discourage walking. But in this case, only studies that track actual people over time as they move among actual neighborhoods will yield reliable answers.