Does neighborhood fast-food outlet exposure amplify inequalities in diet and obesity? A cross-sectional study.

BACKGROUND: Greater exposures to fast-food outlets and lower levels of education are independently associated with less healthy diets and obesity. Little is known about the interplay between these environmental and individual factors.

OBJECTIVE: The purpose of this study was to test whether observed differences in fast-food consumption and obesity by fast-food outlet exposure are moderated by educational attainment.

DESIGN: In a population-based cohort of 5958 adults aged 29-62 y in Cambridgeshire, United Kingdom, we used educational attainment-stratified regression models to estimate the food-frequency questionnaire-derived consumption of energy-dense "fast foods" (g/d) typically sold in fast-food restaurants and measured body mass index (BMI; in kg/m(2)) across geographic information system-derived home and work fast-food exposure quartiles. We used logistic regression to estimate the odds of obesity (BMI ≥30) and calculated relative excess risk due to interaction (RERI) on an additive scale. Participant data were collected during 2005-2013 and analyzed in 2015.

RESULTS: Greater fast-food consumption, BMI, and odds of obesity were associated with greater fast-food outlet exposure and a lower educational level. Fast-food consumption and BMI were significantly different across education groups at all levels of fast-food outlet exposure (P < 0.05). High fast-food outlet exposure amplified differences in fast-food consumption across levels of education. The relation between fast-food outlet exposure and obesity was only significant among those who were least educated (OR: 2.05; 95% CI: 1.08, 3.87; RERI = 0.88), which suggested a positive additive interaction between education and fast-food outlet exposure.

CONCLUSION: These findings suggest that efforts to improve diets and health through neighborhood-level fast-food outlet regulation might be effective across socioeconomic groups and may serve to reduce observed socioeconomic inequalities in diet and obesity.