Marital status is related to morbidity and mortality, with married people healthier and at lower risk of death than those who are unmarried (especially among men). However, the relationship between marital status and obesity is not well established. Role theory suggests through a marital causation model that people in the marital role are more likely to be obese, and through a marital selection model that people in the marital role are less likely to be obese because of stigmatization. The martial causation model was examined using data from the National Survey of Personal Health Practices and Consequences, a cross-sectional national telephone survey of 3025 adults age 20-64 in the United States. Sequential regression analyses revealed that married men were significantly fatter and more likely to be obese than never married or previously married men, even when demographic, social, and physical variables were controlled. By contrast, marital status was not significantly associated with fatness or obesity among women when other variables were controlled. The marital role appears to influence fatness and obesity among men, but not women.