Objective: To identify the factors associated with geographic variations in Body Mass Index (BMI) and obesity in Spain.
Design: Cross-sectional, ecological analysis using data on illiteracy rate (per 1000 population), energy intake (kcal/person/d), sedentary population (%), smoking population (%), alcohol consumption (g/person/d), and percentage of population aged 65 y or over, for Spain's 50 provinces.
Subjects: Non-institutionalized population aged 16y or over.
Measurements: Median BMI and percentage of population with obesity, defined as BMI > 30 kg/m2.
Results: There was a clear geographical pattern, with some areas in the south and north-west of the country registering the highest BMI and prevalence of obesity and a north-south pattern on illiteracy per 1000 population. Multivariate regression analysis showed that illiteracy, sedentary lifestyle and energy intake explain 35% and 14% of the variation in BMI and obesity, respectively. Illiteracy proved to be the variable most associated with both BMI (regression coefficient (beta = 0.01; P = 0.005) and obesity (beta = 0.05; P = 0.013). Sedentary lifestyle showed a statistically significant relationship with BMI (beta = 0.01; P = 0.03), but not with obesity (beta = 0.03; P = 0.581). Energy intake exhibited a relationship with BMI (beta < 0.01 P = 0.03) that lost statistical significance when adjusted for age.
Conclusion: Geographical variations in BMI in Spain are partly explained by illiteracy, sedentary lifestyle and, to a lesser extent, energy intake, whereas regional variations in obesity are related only to the educational level of the population.