ObjectiveTo assess the association between midlife body mass index (BMI) and healthy aging (HA) in the French SU.VI.MAX cohort. MethodsHA was assessed in 2007 to 2009 among 2,733 individuals, aged 45 to 60 years and free of diabetes, cardiovascular disease and cancer at baseline (1994-1995). HA was defined as not developing any major chronic disease, good physical and cognitive functioning, no limitations in instrumental activities of daily living, no depressive symptoms, no health-related limitations in social life, good overall self-perceived health, and no function-limiting pain. Associations between anthropometric indicators (measured in 1995-1996) and HA were assessed using robust-error-variance Poisson regression. ResultsAfter adjustment for potential confounders, BMI (continuous) was negatively associated with HA: relative risk (RR)=0.97 (95% confidence interval = 0.96-0.99). Moreover, the detrimental role of obesity (RRobesity vs. normal weight=0.67 [0.51-0.88]) was substantially stronger than that of overweight (RRoverweight vs. normal weight=0.91 [0.81-1.01]). Furthermore, while metabolically healthy individuals with overweight had a similar HA probability as metabolically healthy individuals with normal weight, metabolically unhealthy overweight individuals had a substantially lowered HA probability. ConclusionsThis study provides novel evidence that an elevated BMI at midlife may jeopardize the preservation of health during aging. Our results also highlight the importance of maintaining a healthy metabolic profile during midlife.