This paper aims to contribute to the debate on the North–South health divide, by disentangling the conditioning factors that account for regional differences in BMI. Based on the Spanish data of the European Health Survey of 2014, we first decompose the average BMI gap between the North and the South of Spain into the contribution of the explained and unexplained factors, using the Oaxaca-Blinder decomposition. We also carry out a distributional analysis by applying the Recentered Influence Function (RIF) Regression and the corresponding decomposition, to analyse BMI differentials along its unconditional distribution. We consider the case of Spain, which is a country characterized by important geographical disparities in BMI and other health outcomes, as well as by the decentralized structure of the Spanish National Health System (NHS). Indeed, this is the first paper that estimates and decomposes the underlying factors responsible for regional BMI variation in European countries. Our findings indicate that North to South differences in mean BMI are significant only for women and a large share (64%) of this gap is explained by differences in endowments (basically years of schooling) to the detriment of women living in the South. Moreover, the explained (unexplained) portion of the gap steadily increases (decreases) along the BMI distribution, revealing that what really matters to deal with the obesity epidemic among overweight women is focusing attention on regional disparities in endowments, human capital being the main driver.