High dietary inflammatory index is associated with an increased risk of overweight and obesity in adults: a meta-analysis of observational studies.

BACKGROUND AND

OBJECTIVE

Unhealthy dietary patterns are recognized risk factors for obesity by promoting chronic low-grade inflammation. This meta-analysis aimed to examine whether higher DII scores are associated with overweight/obesity in adults.

METHODS

PubMed, Embase, ScienceDirect, Cochrane Library, and Web of Science databases were searched up to April 16, 2025. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were pooled for the highest versus lowest DII.

RESULTS

A total of 22 studies were included, comprising 19 cross-sectional studies and three prospective cohort studies. Meta-analysis of the cross-sectional studies indicated a small but significant positive association between DII and BMI (Cohen's d = 0.17; 95% CI: 0.09, 0.25), with significant heterogeneity (Q test, p < 0.001; I 2 = 85.7%). After excluding one study identified by leave-one-out sensitivity analysis, the pooled effect size increased slightly and heterogeneity significantly decreased (Cohen's d = 0.20; 95% CI: 0.17, 0.23; Q test, p = 0.032; I 2 = 42.0%). Meta-regression analysis indicated that publication year and WHO regions partially explained heterogeneity (p = 0.016; p = 0.004), whereas subgroup analyses revealed only publication year as statistically significant (p = 0.040). Cohort studies generally suggested a positive association between DII and BMI (RR = 1.59, 95% CI: 0.72, 3.50; β = 0.41, 95% CI: 0.21, 0.61; HR = 1.32, 95% CI: 1.08, 1.60).

CONCLUSION

Higher DII is associated with overweight/obesity. Further studies are needed to clarify the temporal relationship and underlying biological mechanisms linking dietary inflammatory potential with overweight/obesity.

SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251049098, Identifier: CRD420251049098.