Effects of family life cycle events on individual Body Mass Index trajectories: Evidence from China

Purpose: Body mass index (BMI) is an important predictor of one's physiological health. China is a family-centric nation compared to Western societies and has already entered an aged society. Exploring the characteristics and patterns of BMI changes during household events in China provides critical insights into the biological and social determinants of health, which can help enhance the scientific validity of health promotion measures and contribute to the realization of healthy aging goals in China. Methods: Using data from the China Health and Nutrition Survey (CHNS) from 1993 to 2015, this article utilizes two-level growth curve models with piecewise spline specifications for age to examine the effects of family life cycle events on BMI trajectories for age groups and gender differences. Results: Compared to continuing status, experiencing transition in an individual's family life cycle could lead to more fluctuating variations in their BMI trajectories, generally, there is a faster increase in BMI during youth and a faster decline during old age. As for gender heterogeneity, males are more affected by divorce, widowhood, and empty nest, whereas females' BMI changes are influenced by entering/maintaining marriage and parenthood. Conclusions: A long-term perspective has revealed the significance of family events on BMI throughout the life course. Future research should focus on the nutrition and health of specific populations, especially elderly individuals in vulnerable groups.