Chronotype, Sleep Quality, and Depression as Psychobiological Determinants of Mediterranean Diet Adherence in Overweight and Obese Adults: Cross-Sectional Study

Objective: Psychobiological factors such as chronotype, sleep quality, and depression may influence adherence to the Mediterranean diet, particularly among overweight or obese adults. This study aimed to examine the direct and indirect effects of these factors on dietary adherence. Material and Methods: This cross-sectional study included 300 overweight or obese adults who applied to private diet counseling centers in Fethiye. Participants were assessed using the Mediterranean Diet Adherence Screener (MEDAS), the MorningnessEveningness Questionnaire, the Pittsburgh Sleep Quality Index, and the Beck Depression Inventory. The data were analyzed using the MannWhitney U test, Spearman's correlation, regression, and mediation analyses. Results: According to the regression analysis, MEDAS scores were significantly predicted by older age B=0.038, 95% confidence interval (CI) (0.016 to 0.061), morning chronotype B=0.046, 95% CI (0.018 to 0.074), and female gender B=-0.539, 95% CI (-1.034 to - 0.044) (R²=0.146, p<0.001). Mediation analyses indicated that eveningness partially mediated the associations between depression, sleep quality, and dietary adherence. Although the direct effects of depression and sleep quality were not significant, all models demonstrated significant indirect effects through eveningness. The strongest indirect pathway was observed for subjective sleep quality (indirect effect= -0.321, 95% CI excluding zero). Conclusion: These findings may inform future research and practice by supporting the development of personalized nutrition strategies that consider chronotype, sleep quality, and depressive symptoms. Further longitudinal and interventional studies are warranted to explore causal pathways and confirm these associations across diverse populations and cultural contexts.