Supplementary Material for: Association between the dietary inflammatory index and all-cause mortality in adults with obesity

Introduction: The dietary inflammatory index (DII) is associated with numerous chronic non-communicable diseases. Previous studies have shown that the pro-inflammatory DII categories are associated with abdominal and simple obesity. However, the association between DII and mortality in patients with abdominal obesity and simple overweight or obesity remains unclear. Methods: We used data from the United States National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018. A DII >0 (positive DII) was defined as a pro-inflammatory diet. A restricted cubic spline curve was used to describe the trend between DII and all-cause mortality. We then examined the association between DII and all-cause mortality in different body types using a Cox regression analysis and investigated the differences between sexes. Finally, the mediating effects of systemic inflammation were explored. Results: A pro-inflammatory diet increased all-cause mortality in adults with abdominal obesity (aHR: 1.31, 95% CI: 1.11–1.54; P<0.001) and with simple overweight or obesity (aHR: 1.30, 95% CI: 1.11–1.53; P<0.001). In addition, the most pro-inflammatory DII increased the risk of mortality by 43 % (HR: Q4 vs Q1 = 1.43, 95% CI = 1.14–1.79; P=0.002; P for trend=0.003) and 39 % (HR: Q4 vs Q1 = 1.39, 95% CI = 1.13–1.74; P=0.003; P for trend=0.009) in participants with abdominal obesity and with simple overweight or obesity, respectively. However, this association was not present in normal-sized participants. Compared with men, women resisted the effects of a pro-inflammatory diet. Mediation analysis showed that white blood cell and neutrophil were mediators of the association between DII and all-cause mortality (P<0.001). Conclusion: A pro-inflammatory diet is associated with all-cause mortality in adults with abdominal obesity and simple overweight or obesity, and this effect differs between men and women. Systemic inflammation may mediate the association between DII and all-cause mortality.