PURPOSE: We assessed whether longitudinal changes in body mass index (BMI) are positively associated with changes in 10-year American College of Cardiology/American Heart Association atherosclerotic cardiovascular disease (ASCVD) risk scores in middle-aged blacks compared to whites. METHODS: Data were from 1691 participants enrolled in the Coronary Artery Risk Development in Young Adults Study aged 40 years or more in 2000-2001, who had follow-up examinations 5 and 10 years later. RESULTS: The prevalence of obesity increased from 32.3% in 2000-2001 (mean age: 42.8 years) to 41.7% in 2010-2011, higher in blacks than whites. The corresponding change in 10-year ASCVD risk was significantly higher for blacks (men: 4.5%-9.6%, women: 1.7%-5.0%) than whites (men: 2.4%-5.2%, women: 0.7%-1.6%). In 2010-2011, 57.5% of black men had ASCVD risk scores of 7.5% or more compared to white men (14.7%), black women (17.4%), and white women (1.6%). Although BMI trends were positively associated with 10-year change in ASCVD risk scores (0.07% per 1 kg/m(2) increase), it explained very little variance in risk score trends in all race-sex groups. CONCLUSIONS: In middle-aged adults, longitudinal changes in BMI had little independent influence on changes in 10-year ASCVD risk scores as its effect may be largely mediated through ASCVD risk factors already accounted for in the risk score.