Obesity is widely recognized as a health risk, but it also represents a disadvantaged social position. Viewing body weight within the framework of stigma and its effects on life chances, we examine how perceived weight-based discrimination influences identity and physical health. Using national survey data with a 10-year longitudinal follow-up, we consider whether perceptions of weight discrimination shape weight perceptions, whether perceived weight discrimination exacerbates the health risks of obesity, and whether weight perceptions are the mechanism explaining why perceived weight discrimination is damaging to health. Perceived weight discrimination is found to be harmful, increasing the health risks of obesity associated with functional disability and, to a lesser degree, self-rated health. Findings also reveal that weight-based stigma shapes weight perceptions, which mediate the relationship between perceived discrimination and health. (Contains 5 tables and 8 footnotes.)