Decomposing cross-country differences in levels of obesity and overweight: does the social environment matter?

A key question underpinning health production that remains relatively unexplored is the influence of socio-economic and environmental factors on weight gain and obesity. Such issues acquire particular relevance when data from two Mediterranean countries (Italy and Spain) are compared. Although the obesity rate was roughly the same in the two countries in 1990, by 2003 it was five percentage points higher in Spain than in Italy. This paper reports a non-linear decomposition of differences in the prevalence of overweight and obesity in Spain and Italy by gender and age. We isolate the influence of lifestyle factors and socio-economic and environmental effects in explaining cross-country differences. Our findings suggest that when the social environment (peer effects) is not controlled for, eating habits and education are the main predictors of total cross-country differences (36% to 52%), although these two factors have a different impact depending on gender and age. However, when we control for the social environment, these factors lose their explanatory power and peer effects are found to explain between 46% and 76% of cross-country differences and to rise with age.