This study focuses on associations between schooling, income, and body mass index (BMI). The analyses are based on data from 3,963 public university employees in Rio de Janeiro, Brazil, participating in phase 1 of a longitudinal study (the Pró-Saúde Study). ANOVA, Wald test, and generalized linear models were used to analyze differences between subgroups. Obesity prevalence was inversely associated with schooling, especially among women (p < 0.001). In regression analyses, schooling and per capita income were not associated with BMI among men. In women, schooling but not income was significantly and inversely associated with BMI (p < 0.001). Thus, low schooling plays an important role in the social determination of obesity, especially among women.