The intensive margin of food access and its association with health outcomes: evidence of heterogeneous effects across U.S. Communities

We examine how the local food environment relates to health by shifting attention from the extensive margin (counts of food outlets) to the intensive margin, measured by the sales share of healthful retailers. Using a large national establishment dataset merged with tract-level health outcomes, we construct a sales-based healthfulness index of tract-level food environments and estimate its relationship with obesity, diabetes, high blood pressure, mental health issues, and depression of residents. We apply double/debiased machine learning with cross-fitting to flexibly adjust for high-dimensional socioeconomic and built-environment covariates and to separate intensive-margin access from overall retailer density. We find that higher healthful food-sales shares are positively associated with improved health outcomes; a 10-point increase in the healthful food sales share is associated with a 0.87 percentage-point lower obesity prevalence, a 0.19 percentage-point lower diabetes prevalence, and a 0.61 percentage-point lower high blood pressure prevalence, with similar improvements in mental health issues and depression. These associations are heterogeneous across baseline food environments: cardiometabolic outcomes respond most strongly in low-access tracts, while mental health improvements are larger in mid- and high access communities.