Body mass index as a mediator of the relationship between Dietary Inflammatory Index and depression in diabetes: Evidence from the National Health and Nutrition Examination Survey

This study examined the association between the Dietary Inflammatory Index (DII) and depression in individuals with diabetes while investigating body mass index’s (BMI) potential mediating role. DII quantifies diet-induced inflammation, which may worsen neuroinflammation and metabolic disturbances in diabetic patients, potentially elevating the risk of depression. We analyzed data from 4783 participants in the National Health and Nutrition Examination Survey (2009–2023) using generalized linear models to assess DII’s effect of DII on depression in patients with diabetes. Mediation analysis was used to evaluate BMI’s role of BMI in the DII–Patient Health Questionnaire-9 relationship. The prevalence of depression among the diabetic participants was 32.41% (n = 1550). Higher DII scores significantly predicted an increased risk of moderate (odds ratio [OR] = 1.110, 95% confidence interval [CI] = 1.034–1.193, P = .004), moderately severe (OR = 1.117, 95% CI = 1.036–1.247, P = .010), and severe depression (OR = 1.178, 95% CI = 1.018–1.364, P = .028), along with elevated Patient Health Questionnaire-9 scores (OR = 1.108, 95% CI = 1.020–1.204, P = .016). BMI mediated 11.0% of this association (effect = 0.011; 95% CI = 0.001–0.022). Pro-inflammatory diets increased the risk of depression in adults with diabetes across moderate-to-severe categories, with BMI partially explaining this relationship. Clinical management should consider monitoring dietary inflammation and BMI reduction as potential depression prevention strategies in this population.