Fat City: Questioning The Relationship Between Urban Sprawl and Obesity

Posted by: Chris Steins
Thanks to: Peter Gordon's Blog

27 October 2006 - 9:00am

Researchers at the University of Toronto conclude that linking sprawl and obesity is misguided.

From the abstract:

"We study the relationship between urban sprawl and obesity. Using data that tracks individuals over time, we find no evidence that urban sprawl causes obesity. We show that previous findings of a positive relationship most likely reflect a failure to properly control for the fact the individuals who are more likely to be obese choose to live in more sprawling neighborhoods. Our results indicate that current interest in changing the built environment to counter the rise in obesity is misguided."

From the conclusion:

"It has been widely observed that urban sprawl is associated with higher rates of obesity. This observation has led many researchers to infer that urban sprawl causes obesity. The available evidence does not, in fact, permit this conclusion. The higher observed rates of obesity associated with urban sprawl are also consistent with the sorting of obese people into sprawling neighborhoods. In this paper we conduct an analysis which permits us to distinguish between these two possibilities.

Our results strongly suggest that urban sprawl does not cause weight gain. Rather, people who are more likely to be obese (e.g., because they have an idiosyncratic distaste for walking) are also more likely to move to sprawling neighborhoods (e.g., because they can more easily move around by car). Of course the built environment may still place constraints on the type of exercise that people are able to take or the nature of the diet that they consume. The key point is that individuals who have a lower propensity to being obese will choose to avoid those kinds of neighborhoods. What if they are not always able to avoid those neighborhoods because (say) their choice is constrained for financial reasons? Our results suggest that, even then, individuals adjust their exercise and diet to avoid gaining weight. Overall, we find no evidence that neighborhood characteristics have any causal effect on weight."

Contributing authors include: Jean Eid, University of Toronto, Henry G. Overman, London School of Economics, Diego Puga, Universitat Pompeu Fabra, Matthew A. Turner, University of Toronto

Full Story: Fat City: The Relationship Between Urban Sprawl and Obesity (PDF, 150KB)

Source: University of Toronto, Department of Economics, October 24, 2006

More complex model exists.

Submitted by Dano on Sun, 10/29/2006 - 11:09.

An econ pair out of Corvallis published a paper last November that showed that people DO self-select to auto-dependent environments. The paper developed an equation that folks did the "drive 'til you qualify" thing, and then made the time trade-off into the car and away from exercise.

That's why the market is a poor choice to plan all of our communities - the externalities (in this case, obesity).

6. DISCUSSION AND CONCLUSIONS

Our model also emphasizes the interaction through housing markets of land development and weight. When food is a necessary good relative to calorie expenditure, residents who gain more weight are compensated through the market with more housing at a lower per-unit price. In this case, the utility of these residents is reduced by their greater weight gain and their consumption of less food. In equilibrium, these residents live in larger houses to raise their utility to the equilibrium level. As in the hedonic literature on environmental disamenities, the housing market adjusts to reflect the adverse effects of locations with high weight penalties. However, when food is a luxury good relative to calorie expenditure, weight raises the utility of food. In this case, residents who gain the most weight may consume the most food and live in smaller houses in equilibrium. In effect, the housing market adjusts to penalize, rather than compensate, individuals for weight gain.

[. . .]

The urban planning/public health literature emphasizes the adoption of urban design features that lower barriers to physical activity. We present a version of our model in which calorie expenditure costs are an endogenous function of housing density. Our results indicate that the market will produce high-density neighborhoods with low costs of calorie expenditure, but will tend to do so only in locations close to the city center. Farther away, the balance tips in favor of more housing at the expense of higher costs of calorie expenditure. Some have argued that municipal codes prevent the construction of high-density, mixed-use, and walkable neighborhoods (Levine, 1998). Our results suggest that an unfettered market will produce some neighborhoods with these characteristics, but will also yield neighborhoods with features typical of the modern suburb...

Best,

A more complex model needed

Submitted by Miles on Sat, 10/28/2006 - 11:41.

The argument for self selection is reasonable, if the binary choice is being debated (does physical infrastructure cause obesity, or does obesity lead to infrastructure choices).

But is that likely to be the whole story?

What if growing up in car-burbs leads obesity inducing habits AND the choice to live in car-burbs?

What if people self sort to car dependent environments... but then find it more difficult to recover from obesity once they are there?

There are so many more complex and multi-causal relationships that may be involved here that answering the first level question about causation doesn't really end the discussion at all.

A car dependent life, with minimal requirements for daily exercise and lots of processed high fat high sugar food, is still going to be connected to obesity, and the physical infrastructure of suburbia is still going to be implicated in that life....

Miles Hochstein
PortlandGround.com

Portland Ground: Photographs of Portland Oregon

Obesity and Sprawl

Submitted by Manny Grove on Fri, 10/27/2006 - 12:02.

At least a generation ago, there was a painful joke about the causes of suicide. Was it abject poverty, incurable illness, economic collapse, discrimination, simple rejection, bad luck or some obviously lethal combination of the above that caused the collapse of life?

In a world where polysyllabic phrasings seem to have a life of their own, it is hard to top the "idiosyncratic distaste for walking" explanation. I wish I'd thought of it. But so would advertising-induced chemical dependency, isolation and alienation from two-hour commutes, and, my favorite, internalized and misdirected anger and aggression. After all, the only target we are sure to hit is our self, unless one can create a situation in which the police make the final decision.

While I am pleased that the topic has sparked so much interest, I can only hope that I can get some help with my problem:
EDS or environmentally deficient syndrome.
If another stand of trees on the edge of town turns into another Storybook Estates and Golf Links, there's a good chance I might become a tad idiosyncratic myself. And we all know what that will do.

reads like it was written in a different country

Submitted by Michael Lewyn on Fri, 10/27/2006 - 08:29.

This study asserts that "people who are more likely to be obese (e.g. because they have an idiosyncratic distaste for walking are more likely to move to sprawling neighborhoods."

If we lived in a country where only a few people (a) were obese or (b) lived in sprawling neighborhoods, this "finding" might make sense. But realistically, something close to the majority of Americans are overweight, and more importantly, sprawl is where the majority of people (or at least the majority of married people) live. In Jacksonville (where I live) sprawl is the ONLY choice, except for a few small neighborhoods.

So the notion that sprawling areas are dominated by a few people with "idiosyncratic" tastes simply beggars belief. In the America I live in, it is the people who are willing to walk who are "idiosyncratic."