Determinants of geographical variations in body mass index (BMI) and obesity in Spain

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 percenta ge of population aged 65 y or over, for Spain's 50 provinces. SUBJECTS: Non-institutionalized population aged 16 y or over. MEASUREMENTS: Median BMI and percentage of population with obesity, defined as BMI > 30 kg/m(2). RESULTS: There was a clear geographical pattern, with some areas in the sou th and north-west of the country registering the highest BMI and prevalence of obesity and a north-south pattern on illiteracy per 1000 population. Mu ltivariate 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 bot h BMI (regression coefficient (beta = 0.01; P = 0.005) and obesity (beta = 0.05; P = 0.013). Sedentary lifestyle showed a statistically significant re lationship 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, wh ereas regional variations in obesity are related only to the educational le vel of the population.