Association between the dietary inflammatory index and obesity in otherwise healthy adults: Role of age and sex

Aim The dietary inflammatory index (DII) can estimate the overall inflammatory potential of diet. This study aimed to assess the association between DII score and other diet quality parameters with weight status among normal weight, overweight and obese otherwise healthy adults. Methods This retrospective observational study investigated DII, energy-adjusted DII (E-DIITM), dietary energy density (DED) and mean adequacy ratio (MAR) scores, based on a valid 168-item food frequency questionnaire, in 100 normal weight, 100 overweight and 100 obese healthy adults (age > 18yr). Results Normal-weight participants had higher DII scores than obese participants (mean difference (MD): 0.67, 95% confidence interval (CI): 0.004 - 1.33, P = .048). Body mass index (BMI) had an effect on DII score after adjusting for age (P = .03). A statistically significant interaction was observed between BMI and age on E-DII (P = .03) and MAR (P = .004). E-DII scores were lower (more anti-inflammatory) and MAR was higher with increasing age in the obese compared with normal-weight participants. Additionally, male participants had higher DII (MD: -0.53, 95% CI: -0.97 - -0.09, P = .02), E-DII (MD: -0.76, 95% CI: -1.12 - -0.35, P < .001), DED (MD: -0.09, 95% CI: -0.15 - -0.03, P = .004) and lower MAR (MD: 0.04, 95% CI: 0.02 - 0.06, P = .001), after adjusting for BMI. Obesity (Adjusted odds ratio (AOR) = 0.48, 95% CI: 0.26 - 0.91, P = .02) and DED (AOR =5.81, 95% CI: 2.28 - 14.81, P < .001) were the most important factors associated with high DII. Conclusions This study showed that having a normal body weight is not necessarily indicative of less inflammatory potential of diet and better diet quality. Male sex and increasing age were important determinants of diet quality across BMI subgroups.