The income-body-size gradient among Chinese urban adults: A semiparametric analysis

- We estimate the effect of income on adult body size in urban China through semiparametric analysis.
- The income-body size gradient is gender specific and very nonlinear in urban China.
- We emphasize a reversal in the gradient with higher body size being progressively observed among poorer adults.
- The reversal of the income-body-size gradient is observed only for women.
- Deviations from this near-universal reversal path are possible, particularly in the two tails of the income distribution.

The literature has emphasized the existence of a transition in the SES-obesity gradient when a country moves from low-income status to high-income status. As a middle-income country experiencing strong socio-economic changes, China provides a relevant case study. This article forms part of the literature on the impact of SES on body size and aims to clarify and update information about the relationship between income (one specific dimension of SES) and adult body size in urban China. To analyze this potentially complex relationship, we rely on semiparametric methods that enable us to leave the nature of the association between income and body size unspecified in the regression analysis. Empirical investigations conducted as part of this research are based on longitudinal data from the China Health and Nutrition Survey covering the period 1991-2011. Our results show that the income-body size relationship remains complex, gender-specific and very non-linear in urban China. We also provide evidence of the reversal of the income-body-size gradient, a reversal that is observed only for women for the period under study. Finally, we emphasize the specific features of the gradient for the two tails of the income distribution which could indicate that local deviations from the near-universal reversal path are possible.