Urban sprawl not to blame for obesity

Henry Overman, Diego Puga, Matthew Turner, Thu, 04/19/2007

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The industrialised world is getting fatter and the United States is leading the trend. In the late 1970s in the US, 12.7% of men and 17% of women were medically obese; in 2000 these figures had increased to 27.7% and 34% respectively. However, neither the portion of the population that is obese nor the rates of increase in these numbers are geographically evenly distributed. Between 1991 and 1998 the obesity rate increased by 102% in Georgia and only 11% in Delaware. Could these large spatial differences be attributed to the built environment? The existing research suggests that they are, but for this study, the authors used innovative data analysis that suggests otherwise. They found that obesity is correlated with, but not caused by, the choice to live in a sprawling neighbourhood. The idiosyncratic choices that affect obesity, such as a distaste for walking as opposed to driving, also affect neighbourhood choice, explaining geographical discrepancies in obesity rates.

CEPR DP6191 tracks the data of nearly 6,000 people over a six-year study period. During this period 79% of the subjects changed addresses. These movers allowed the authors to identify the effect of sprawl on weight. Sprawl is defined as neighbourhoods with low density and/or walkability and scarce mixed-use developments, specifically retail-outlets and churches. The researchers looked at whether an individual will gain weight when they move to a more sprawling neighbourhood or lose weight when they move to a less sprawling one. This method contrasts with the existing research that documents a correlation between sprawl and obesity but neglects to determine a causal relationship.

It has already been widely observed that urban sprawl is associated with higher rates of obesity, leading many to assume that sprawl itself is the cause. The paper concludes that people who are more likely to be obese are more likely to move to sprawling neighbourhoods. The debate over obesity is ideologically charged and these results are likely to be controversial and (in some circles) unpopular. The findings suggest that the public-health battle against obesity is better fought on ground other than the urban-planner's drawing board.

DP6191 Fat City: Questioning the Relationship Between Urban Sprawl and Obesity

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URL:  www.cepr.org/DP6191

Topics:  Migration

Tags:  obesity, urban sprawl

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