The relationship between Marriage and Body Mass Index in China：Evidence from the China Health and Nutrition Survey

This study investigates the impact of marriage on the body mass index (BMI) of individuals aged 18–45 in China. We used data from ten rounds of the China Health and Nutrition Survey spanning from 1989 to 2015, and applied Difference-in-Differences (DID) model to examine the impact of marriage on BMI. Our findings reveal that marriage has a significant positive effect on BMI, especially among males, with post-marriage elevation of male BMI continuing to increase over time. Moreover, marriage is associated with a 5.2% increase in the prevalence of overweight and a 2.5% rise in the incidence of obesity among males. While energy intake levels for Chinese women did not undergo significant changes after marriage, nor did their energy expenditure levels, men experienced a marked alteration in energy balance, characterized by an increase in caloric intake and a decrease in physical activity. Furthermore, our study confirms significant period differences in the effect of marriage on BMI, with post-marriage elevation of male BMI continuing to rise over time. In contrast, there was no clear trend for female BMI after marriage. Our research highlights the importance of promoting physical fitness and health management within families while fostering intimate relationships through marriage. Public health policies should consider the potential impact of marriage as an intervention window for addressing individuals' weight management needs. Distinct post-marriage body management plans should be designed for both genders.