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 < or =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 < or = 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 < or = 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.