Background: Our objective was to quantify to what extent the association between adherence to the French nutritional recommendations at midlife, measured by the Programme National Nutrition Sante-Guideline Score (PNNS-GS), and healthy aging (HA) is mediated by body mass index (BMI) status. Methods: We analyzed data from 2249 participants of the French 'Supplementation with Vitamins and Mineral Antioxidants' (SU.VI.MAX-'SUpplementation en Vltamines et Mineraux AntioXydants') cohort. At baseline (1994-1995), data on BMI status (<25 vs. >= 25 and <30 vs. >= 30) and diet were collected. At follow-up (2007-2009), HA status (yes/no) was evaluated via a multidimensional concept focusing on chronic disease incidence, physical and cognitive functioning, mental and social health, pain, and perceived health. Relative risks (RR) were estimated by extensively adjusted robust-error-variance Poisson regression, and counterfactual-based mediation analysis was performed. Results: Our HA criteria were met by 39% of participants. We identified a positive direct relation of a greater adherence to the French nutritional recommendations, with the probability of HA (RRQuartile 4 vs. quartile 1 = 1.31 (95% confidence interval (CI) = 1.13, 1.53)), and an indirect relation mediated by BMI status (1.01 (95% CI: 1.01, 1.02)), accounting for 5% of the total relation. Conclusion: These results indicate that high dietary quality may contribute to the preservation of overall health during aging, partly via obesity prevention and partly via other mechanisms.