The 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 November 2009 Abstract. We investigate how changes in the supply of fast-food restaurants affect weight outcomes of 3 million children and 3 million pregnant women. Among 9th graders, a fast-food restaurant within .1 mile of a school results in a 5.2% increase in obesity rates. Among pregnant women, fast-food restaurant within .5 mile of residence results in a 1.6% increase in the probability of gaining over 20 kilos. The implied effects on caloric intake are one order of magnitude larger for children than for mothers, consistent with smaller travel cost for adults. Non-fast-food restaurants and future fast-food restaurants are uncorrelated with weight outcomes. 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 (Mair et al. 2005.)1 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 effect of increases in the local supply of fast-food restaurants on obesity rates. Using a new dataset on the exact geographical location of restaurants, we ask how proximity to fast-food restaurants 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 models with and without school fixed effects. 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. The design employed in this study allows for a more precise identification of the effect of fast-food restaurants 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 groups. Since a fast-food restaurant’s location might reflect characteristics of the area, we test 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 1 Abdollah, Tami. “A Strict Order for Fast Food,” Los Angeles Times, A-1, Sept. 10, 2007, http://articles.latimes.com/2007/sep/10/local/me-fastfood10. See also Mcbride, Sarah. “Exiling the Happy Meal,” Wall Street Journal, July 22, 2008, http://online.wsj.com/article/SB121668254978871827.html Accessed on Nov 9, 2009.2many previous studies: The 9th graders are exposed to fast-food restaurants 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 proximity of fast-food restaurants 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 to substitution 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.2 Ultimately, the effect of changes in the proximity of fast-food restaurants 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 restaurant at .25 miles. This effect amounts to a 5.2 percent increase in the incidence of obesity among the affected children. Since grade 9 is the first year of high school and the fitness tests take place in the spring, the period of fast-food exposure that we measure is approximately 30 weeks, implying an increased caloric intake of 30 to 100 calories per school-day. We view this as a plausible magnitude. The effect is larger in models that include school fixed effects. Consistent with highly non–linear transportation costs, we find no discernable effect at .25 miles and at .5 miles. Among pregnant women, we find that a fast-food restaurant within a half mile of a residence results in a 0.19 percentage points higher probability of gaining over 20 kilograms (kg). This amounts to a 1.6 percent increase in the probability of gaining over 20 kilos. The effect increases monotonically and is larger at .25 and larger still at .1 miles. The increase in