Decomposing Cross-Country Gaps in Obesity and Overweight: Does the Social Environment Matter?

A key question underpinning health production, and one 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. Interestingly, the obesity rate was 5 percentage points higher in Spain in 2003 while in 1990 it had been roughly the same in the two countries. This paper reports a non-linear decomposition of gaps in overweight (body mass index BMI - between 25 and 29.9 kg/m2), class 1 (BMI30 kg/m2) and class 2 obesity (BMI35 kg/m2) between Spain and Italy by both gender and age. We isolate the influence of lifestyles, socioeconomic and environmental effects in explaining cross-country gaps in the prevalence of obesity. 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 gaps (36-52%), albeit that these two factors have a different impact depending on gender and age. Somewhat paradoxically, however, when we controlled for the social environment, these previous predictors lost their explanatory power and peer effects were found to explain between 46 and 76% of gaps and to exhibit an increasing age pattern.