Poverty, Sprawl, and Restaurant Types influence Body Mass Index of Residents in California Counties

Objectives. This article examines the relationships between structural poverty (the proportion of people in a county living at <= 130% of the federal poverty level [FPL]), urban sprawl, and three types of restaurants (grouped as fast food, chain full service, and independent full service) in explaining body mass index (BMI) of individuals. Methods. Relationships were tested with two-tiered hierarchical models. Individual-level data, including the outcome variable of calculated BMI, were from the 2005, 2006, and 2007 California Behavioral Risk Factor Surveillance Survey (n=14, 205). County-level data (n=33) were compiled from three sources. The 2000 U.S. Census provided the proportion of county residents living at <= 130% of FPL and county demographic descriptors. The sprawl index used came from the Smart Growth America Project. Fast-food, full-service chain, and full-service independently owned restaurants as proportions of the total retail food environment were constructed from a commercially available market research database from 2004. Results. In the analysis, county-level demographic characteristics lost significance and poverty had a consistent, robust association on BMI (p<0.001). Sprawl demonstrated an additional, complementary association to county poverty (p<0.001). Independent restaurants had a large, negative association to BMI (p<0.001). The coefficients for chain and fast-food restaurants were large and positive (p <= 0.001), indicating that as the proportion of these restaurants in a county increases, so does BMI. Conclusions. This study demonstrates the important role of county poverty and urban sprawl toward understanding environmental influences on BMI. Using three categories of restaurants demonstrates different associations of full-service chain and independent restaurants, which are often combined in other research.