MPIDR Working Paper

From early life BMI to later life childlessness: consistency across race/ethnicity and mediation by union formation dynamics in the US NLSY79 cohort

MPIDR Working Paper WP-2021-012, 81 pages.
Rostock, Max Planck Institute for Demographic Research (June 2021)
Revised June 2021. The NLSY79 data used for the present study is publicly available via:
Open Access


Demographic studies on childlessness have typically focused on the social underpinnings of fertility behaviors. However, growing evidence indicates that health during early adulthood, as measured by indicators including body mass index (BMI), predicts population level variation in lifetime fertility. Using the NLSY79 data, we examine the association between BMI during early adulthood and childlessness at age 40+ by race/ethnicity, a major social axis for differences in both BMI and childbearing contexts in the United States. We find that being obese or underweight was consistently linked to higher lifetime childlessness in both sexes, compared to their healthy BMI counterparts, and that this pattern was broadly similar across Hispanic, black and non-Hispanic and non-black groups. Among the obese, but not the underweight, much of the BMI-childlessness association was driven by lower chances to ever marry, and marrying at older ages if marriage occurred. Finally, obese women were more likely to deviate from the common preference for two children, but this difference in fertility preferences played a minor role in the early BMI differentials for childlessness. This study suggests that the influence of early life BMI on childlessness and fertility manifests itself through complex intersections of physiological, psychological, and social/behavioral mechanisms.

Keywords: USA, body weight, completed fertility, desired family size, ethnicity, health, marital union, races, sex differentials
The Max Planck Institute for Demographic Research (MPIDR) in Rostock is one of the leading demographic research centers in the world. It's part of the Max Planck Society, the internationally renowned German research society.