We analyze the influence of body weight in early adulthood, and changes in weight over time, on self-rated health as people age into middle adulthood. While prior research has focused on cross-sectional samples of older adults, we use longitudinal data from the NHANES I Epidemiologic Follow-up Study and double-trajectory latent growth models to study the association between body mass index (BMI) and self-rated health trajectories over 20 years. Results indicate that high BMI in early adulthood and gaining more weight over time are both associated with a faster decline in health ratings. Among white women only, those with a higher BMI at the baseline also report lower initial self-rated health. A small part of the weight-health association is due to sociodemographic factors, but not baseline health behaviors or medical conditions. The findings provide new support for the cumulative disadvantage perspective, documenting the increasing health inequalities in a cohort of young adults.