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The following is a summary of “Association among obesity, insulin resistance, and depressive symptoms: a mediation analysis,” published in the April 2025 issue of BMC Psychiatry by Xiao et al. 

The link between obesity and depressive symptoms is well established, but the role of insulin resistance (IR) in this relationship remains unclear. 

Researchers conducted a retrospective study to examine the link between body mass index (BMI) and depressive symptoms, focusing on the mediating role of insulin resistance. 

They used data from the National Health and Nutrition Examination Survey (NHANES) 2005–2018 and applied multivariate logistic regression, restricted cubic splines (RCS), and subgroup analysis to assess the correlation between obesity and depressive symptoms. Mediation analysis was performed to examine the role of insulin resistance in the relationship. 

The results showed a final sample of 12,744 participants. Obesity was significantly associated with depressive symptoms. Lack of exercise and vigorous activity levels modified this association (P for interaction < 0.05), as did smoking status (P for interaction < 0.05). BMI showed an S-shaped association with depressive symptoms, becoming positive after BMI > 23.22 kg/m² (P < 0.001). IR partially mediated the effect of overweight/obesity on depressive symptoms (54.13%, P = 0.018). 

Investigators confirmed a significant association between obesity and depressive symptoms. They found that insulin resistance partially mediated this link, and that physical exercise and smoking influenced the risk. 

Source: bmcpsychiatry.biomedcentral.com/articles/10.1186/s12888-025-06765-9