# The Dietary Inflammatory Index and Incident Risk of Type 2 Diabetes Mellitus: Interactions with Obesity and Dyslipidemia in a Prospective Cohort Study

## TL;DR

A pro-inflammatory diet may increase type 2 diabetes risk in women, especially when combined with obesity.

## Contribution

Identifies a synergistic effect between a pro-inflammatory diet and central obesity in increasing type 2 diabetes risk.

## Key findings

- High dietary inflammatory index (DII) was linked to increased type 2 diabetes risk in women.
- Central obesity metrics synergized with high DII to elevate diabetes risk.
- No significant interactions were found with dyslipidemia or other obesity measures.

## Abstract

Objectives: To explore the association between the dietary inflammatory index (DII) and type 2 diabetes mellitus (T2DM) risk and to evaluate potential interactions of obesity and dyslipidemia in the context of this association. Methods: This cohort study included 8055 adults. Dietary data from food frequency questionnaires were used to calculate DII, reflecting dietary inflammatory potential. T2DM was defined as fasting plasma glucose ≥7.0 mmol/L, HbA1c ≥6.5%, a documented T2DM history, or glucose-lowering therapy. Multivariate Cox regression models assessed the DII-T2DM association, with multiplicative interaction analysis via product terms and additive interactions evaluated using relative excess risk due to interaction (RERI) and attributable proportion due to interaction (AP). Results: After a median 5.01-year follow-up, 1034 incident T2DM cases had occurred. The highest versus lowest DII quartile showed an unadjusted HR of 1.20 (95% CI: 1.01–1.42), which attenuated after adjusting for demographic and clinical confounders. In women, the highest DII quartile had a significantly adjusted HR of 1.36 (1.03–1.81), with a 16% increased risk per 1-SD DII increase (adjusted HR:1.16, 95% CI:1.04–1.29); no association was observed in men. Positive multiplicative and additive interactions emerged in total participants between high DII and central obesity (measured by waist circumference/waist-to-hip ratio), accounting for 22% and 31% of excess T2DM risk, respectively. No interactions were found with dyslipidemia and other obesity metrics (BMI, waist-to-height ratio). Conclusions: This study suggests that a highly pro-inflammatory diet may be associated with an increased incident risk of T2DM among women. Waist circumference and waist-to-hip ratio and a high DII are found to act synergistically in elevating T2DM risk.