fastfoodoct3.pdfObesFFTables1003Rev.pdfThe Effect of Fast Food Restaurants on Obesity and Weight Gain Janet Currie, Columbia University and NBER Stefano DellaVigna, UC Berkeley and NBER Enrico Moretti, UC Berkeley and NBER Vikram Pathania, UC Berkeley September 2009 Abstract. We investigate the health consequences of changes in the supply of fast food using the exact geographical location of fast food restaurants. Specifically, we ask how the supply of fast food affects the obesity rates of 3 million school children and the weight gain of over 3 million pregnant women. We find that among 9th grade children, a fast food restaurant within a tenth of a mile of a school is associated with at least a 5.2 percent increase in obesity rates. There is no discernable effect at .25 miles and at .5 miles. Among pregnant women, models with mother fixed effects indicate that a fast food restaurant within a half mile of her residence results in a 1.6 percent increase in the probability of gaining over 20 kilos, with a larger effect at .1 miles. The effect is significantly larger for African-American and less educated women. For both school children and mothers, the presence of non-fast food restaurants is uncorrelated with weight outcomes. Moreover, proximity to future fast food restaurants is uncorrelated with current obesity and weight gain, conditional on current proximity to fast food. The implied effects of fast-food on caloric intake are at least one order of magnitude larger for students than for mothers, consistent with smaller travel cost for adults. The authors thank John Cawley, the editor, two anonymous referees and participants in seminars at the NBER Summer Institute, the 2009 AEA Meetings, the ASSA 2009 Meetings, the Federal Reserve Banks of New York and Chicago, the FTC, the New School, the Tinbergen Institute, UC Davis, the Rady School at UCSD, and Williams College for helpful comments. We thank Joshua Goodman, Cecilia Machado, Emilia Simeonova, Johannes Schmeider, and Xiaoyu Xia for excellent research assistance. We thank Glenn Copeland of the Michigan Dept. of Community Health, Katherine Hempstead and Matthew Weinberg of the New Jersey Department of Health and Senior Services, and Rachelle Moore of the Texas Dept. of State Health Services for their help in accessing the data. The authors are solely responsible for the use that has been made of the data and for the contents of this article. 11. Introduction In the public debate over obesity it is often assumed the widespread availability of fast food restaurants is an important determinant of obesity rates. Policy makers in several cities have responded by restricting the availability or content of fast food, or by requiring posting of the caloric content of the meals (Abdollah, 2007; Mcbride, 2008; Mair et al. 2005). But the evidence linking fast food and obesity is not strong. Much of it is based on correlational studies in small data sets. In this paper we seek to identify the causal effect of increases in the supply of fast food restaurants on obesity rates. Specifically, using a detailed dataset on the exact geographical location of restaurants, we ask how proximity to fast food affects the obesity rates of over 3 million school children and the weight gain of 3 million pregnant women. For school children, we observe obesity rates for 9th graders in California over several years, and we are therefore able to estimate cross-sectional as well as fixed effects models that control for characteristics of schools and neighborhoods. In the fixed effects models we focus on the openings of new restaurants and compare the difference in the change over time in obesity rates between schools that are located .1 miles from a new fast food restaurant and schools that are located .25 miles or more from a new fast food restaurant. For mothers, we employ the information on weight gain during pregnancy reported in the Vital Statistics data for Michigan, New Jersey, and Texas covering fifteen years. We focus on women who have at least two children so that we can follow a given woman across two pregnancies and estimate models that include mother fixed effects. In these models, we relate changes in weight gain for a mother between pregnancies to changes in proximity to fast food between the pregnancies. The design employed in this study allows for a more precise identification of the effect of fast-food on obesity than the previous literature. First, we observe information on weight for millions of individuals compared to at most tens of thousand in the standard data sets used previously. This large sample size substantially increases the power of our estimates. Second, we exploit very detailed geographical location information, including distances of only one tenth of a mile. By comparing groups of individuals who are at only slightly different distances to a restaurant, we can arguably diminish the impact of unobservable differences in characteristics between the two 1groups. Moreover, we take the idea that fast food location might reflect characteristics of the area very seriously and test to see whether there are any observable patterns in restaurant location within the very small areas we focus on. Third, we have a more precise idea of the timing of exposure than many previous studies: The 9th graders are exposed to fast food near their new school from September until the time of a spring fitness test, while weight gain during pregnancy pertains to the 9 months of pregnancy. While it is clear that fast food is often unhealthy, it is not obvious a priori that changes in the availability of fast food should be expected to have an impact on health. On the one hand, it is possible that proximity to a fast food restaurant simply leads local consumers to substitute away from unhealthy food prepared at home or consumed in existing restaurants, without significant changes in the overall amount of unhealthy food consumed. On the other hand, proximity to a fast food restaurant could lower the monetary and non-monetary costs of accessing unhealthy food.1 Ultimately, the effect of changes in the supply of fast food on obesity is an empirical question. We find that among 9th grade children, the presence of a fast-food restaurant within a tenth of a mile of a school is associated with an increase of about 1.7 percentage points in the fraction of students in a class who are obese relative to the presence of a fast food