Proximity to Fast Food a Factor in Student Obesity

Ninth graders whose schools are within a block of a fast-food outlet are more likely to be obese than students whose schools are a quarter of a mile or more away, according to a study of millions of schoolchildren by economists at the University of California and Columbia University.

The study, a widely circulated working paper of the independent National Bureau of Economic Research, marks an intensive effort by economists to determine whether close geographic proximity to fast food plays a causal role in obesity.

The sample population was large, spanned almost a decade and included such detailed geographic information that researchers were able to observe obesity rates among ninth graders in the same school in the years before and after a new fast food outlet opened nearby.

After adjusting for a wide range of variables, including income, education and race, the researchers found that obesity rates were 5 percent higher among the ninth graders whose schools were within one-tenth of a mile of a pizza, burger or other popular fast-food outlet, compared with students attending schools farther away from fast-food stores.

"I think we got as close to proving causation as any other study has, and probably as close as is feasible with the existing data," said Enrico Moretti, a professor of economics at the University of California, Berkeley, and one of the paper's authors. "We're quite confident that these are credible and unbiased estimates of the causal effect of fast food on obesity for the group we focused on."

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