Does marriage have a causal impact on weight and the likelihood of becoming obese? Marriage is thought to have a protective influence on both men's and women's health, although via different mechanisms. Evidence in regard to marriage affecting body mass index (BMI) and the propensity to become obese, however, is mixed and often based on limited data. Even less clear is whether the effect varies by race and gender. In this article, the author uses the National Longitudinal Survey of Youth (1979), which has followed individuals for more than 20 years, and uses methods aimed at netting out selection bias to show that marriage is associated with a modest increase in BMI for all race and gender groups. Additionally, marriage is associated with an increase in the likelihood for becoming obese for African American women. (Contains 3 tables and 8 notes.)