Energy-adjusted Dietary Inflammatory Index (E-DII) Mediates the Association between Obesity and Depressive Symptoms: A Population-Based Analysis of NHANES 2007-2018

Epidemiological and clinical research has confirmed a link between obesity and depressive symptoms, with inflammation as a potential common mechanism. Given that dietary components modulate inflammation and relate to both conditions, investigating dietary inflammation as a potential underlying pathway is necessary. Herein, we aimed to explore the potential role of Energy-adjusted Dietary Inflammatory Index (E-DII) in explaining the relationship between obesity and depressive symptoms. We conducted a cross-sectional analysis of the 2007-2018 National Health and Nutrition Examination Survey (NHANES) cohort, enrolling 20,324 participants. Obesity and dietary inflammation were assessed by Body Mass Index (BMI) and E-DII, respectively. Depressive symptoms were evaluated using the nine-item Patient Health Questionnaire-9 (PHQ-9). We found that obesity and inflammatory diets were positively associated with of depressive symptoms (β = 0.50, 95% CI: 0.30-0.69; β = 0.35, 95% CI: 0.19-0.50; both p < 0.001), and variations in the association among obesity, pro-inflammatory diets and depressive symptoms were evident across various population subgroups (e.g sex, age, chronic diseases and smoking status subgroups, p for interaction < 0.050). After adjusting for all covariates, E-DII accounted for 4% of the obesity-depression association. Despite this modest proportion, the finding identifies dietary-induced inflammation as a statistically significant, modifiable pathway. In conclusion, obesity and pro-inflammatory diets are linked to increased risk of depressive symptoms, with E-DII serving as a modest but significant modifiable pathway. These findings highlight dietary intervention as a potential strategy for mitigating depressive symptoms in individuals with obesity.