Association for Public Policy Analysis & Management

Objectives: This study examines the effect of food environments characterized as food swamps on adult obesity. I aim to operationalize the concept of a food swamp, a spatial metaphor comparable to food deserts.  Food swamps have been described as areas that are inundated with high-calorie fast food and junk food relative to healthier food options. In this paper, I present multiple ways of categorizing food environments as county-level food swamps and food deserts. Also, I introduce more comprehensive versions of the Retail Food Environment Index (RFEI) that consider the density of food store outlets in addition to grocery stores and fast food restaurants. Furthermore, I employ an instrumental variables (IV) strategy to correct for the endogeneity problems associated with food environments. More explicitly, individuals self-select into certain neighborhoods and may consider food availability in their decision process. Highway exits have been used as an instrument for fast food access in previous studies. Based on historical evidence dating the start of the system to the 1940s, I exploit highway exits as a source of exogenous variation in order to explore causal links between food swamps and the prevalence of adult obesity.

Methods: Using secondary data from the USDA Food Environment Atlas, ordinary least squares (OLS) and IV regression models were employed to analyze cross-sectional associations between local food environments and the prevalence of obesity. The sample include 3,108 U.S. Counties. I used the number of highway exits per county as an instrument for food environments characterized as food swamps.

Results: I find even after controlling for food desert effects, food swamps have a positive, statistically significant effect on adult obesity rates. All seven food swamp measures indicated the same positive association, but reflected different magnitudes of the food swamp effect on obesity. Also, without adjusting for reverse causality using an IV approach, this effect would have been underestimated by naïve OLS estimates. The food swamp effect remains in counties with higher educational attainment and more income inequality. Finally, food swamps increase obesity by almost 9 percent in counties where more people drive to work.

Conclusions: Preliminary findings provide evidence for zoning strategies to simultaneously restrict access to unhealthy food outlets and incentivize healthy food retailers to locate in underserved neighborhoods. The results of this study suggest that zoning ordinances might establish quotas for the number of fast food restaurants or convenience stores in a municipality or target establishments that make unhealthy foods more convenient for drivers (i.e. drive-thrus).