Lifting the lid on geographic complexity in the relationship between body mass index and education in China.

In China, rising obesity has coincided with increasing affluence. Few studies have properly accounted for geographic variation, however, which may influence prior results. Using large data with biomarkers in China, we show body mass index (BMI) to be positively correlated with higher person-level education if estimated using ordinary least squares. In stark contrast, fitting the same data within a multilevel model gives the complete opposite result. We go on to show that the relationship between BMI and person-level education in China is dependent upon geography, underlining why multilevel modelling is crucial for revealing these types of people-place contingencies.