From Diet to Oxidative Stress: Obesity as a Key Mediator in Postmenopausal Women

Background Oxidative stress plays a critical role in age-related pathophysiology, and postmenopausal women are particularly vulnerable due to hormonal and metabolic changes. Although dietary quality has been implicated in modulating oxidative balance, the potential mediating role of obesity in this relationship remains insufficiently explored. Objectives This study aimed to examine the associations between dietary quality and oxidative stress among postmenopausal women using data from the National Health and Nutrition Examination Survey (NHANES) and to assess whether obesity mediates this relationship. Methods A total of 2,391 postmenopausal women from NHANES cycles 2005–2020 were included. Dietary quality was assessed using the Healthy Eating Index (HEI-2015), Dietary Inflammatory Index (DII), and Composite Dietary Antioxidant Index (CDAI). Oxidative stress status was measured using the Oxidative Balance Score (OBS), while obesity was evaluated using body mass index (BMI) and waist circumference. Weighted multivariable regression and restricted cubic spline models were employed to investigate associations. Mediation analysis was performed to assess the potential mediating role of obesity. Results Higher HEI and CDAI scores were significantly associated with higher OBS, while higher DII was associated with lower OBS (all P < 0.01). Similarly, healthier dietary profiles were inversely associated with both BMI and waist circumference. Obesity indicators were negatively associated with OBS. Mediation analysis suggested that BMI and waist circumference explained a small but statistically significant proportion of the associations between dietary indices and OBS. Conclusions Among postmenopausal women, healthier dietary patterns were associated with more favorable oxidative stress profiles. Obesity may partly mediate these associations. These findings highlight the potential value of dietary and weight management strategies in mitigating oxidative stress in this population, warranting further longitudinal and interventional studies to clarify underlying mechanisms.