The role of spouse is associated with better health. The dynamics of spousal roles can be represented by marital trajectories that may remain stable or may change by entry into marriage, dissolution of marriage, or death of a spouse. Body weight is an important health-related characteristic that has been found to have mixed relationships with marital status. This analysis examined changes in marital status and body weight in 9043 adults in the US National Health and Nutrition Epidemiological Follow-up Survey (NHEFS), a longitudinal national study that interviewed and measured adults in a baseline assessment and reassessed them again in a follow-up approximately 10 years later. Men's and women's weights were differently associated with marital changes. Women who were unmarried at baseline and married at follow-up had greater weight change than those who were married at both times. Analysis of weight loss and weight gain separately revealed that sociodemographic variables, including marital change, were more predictive of variation in weight loss than weight gain. Unmarried women who married gained more weight than women married at both times. Men who remained divorced/separated and men who became widowed lost more weight than men married at both baseline and follow-up. These findings suggest that changes in social roles, such as entering or leaving marriage, influence physical characteristics such as body weight.