Densification and health in China: A U-shaped association between population density and obesity

Densification is a key measure to improve public health in many low-density countries. However, empirical studies show that population density has mixed results on health in different contexts. A possible hypothesis is that the relationship between population density and unhealthiness is a U-shaped curve. This study tested the U-shaped relationship between population density and body mass index (BMI). It employed fixed effects models with longitudinal and nationwide data in China collected between 2012 and 2014, comprising 3,423 observations from 1,984 respondents. After controlling for individuals’ socioeconomic characteristics and other built environmental elements, the results support the hypothesis of the U-shaped association between population density and BMI. Specifically, when population density is low, it is negatively related to BMI. However, when population density is high, it has positive effects on BMI. We further discuss the possible mechanisms and thresholds of the U-shaped effects of population density. The U-shaped relationship between densification and obesity encourages planners to consider local contexts and adopt a moderate population density when planning healthy cities.