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/m2 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.