Association between the systemic immune-inflammation index and obesity among adults: Insights from the NHANES 2017-2018

Background Inflammation is an important causative factor of obesity. This study aimed to explore the possible association between the systemic immune-inflammatory index, a novel indicator of inflammation, and obesity. Methods Data were collected from 4395 participants of the National Health and Nutrition Examination Survey 2017-2018 aged >= 20 years. The systemic immune-inflammatory index was calculated by multiplying the platelet count by the neutrophil-to-lymphocyte ratio. Obesity was defined as a body mass index >= 30 kg/m2. Results A significant positive correlation was observed between the systemic immune-inflammatory index and body mass index following multivariate linear regression analysis (beta = 1.75; 95% confidence interval = 1.16-2.33), which was greatest in adults aged < 60 years without hypertension and diabetes. Smoothed curve fitting and threshold effect analysis were used to characterize the nonlinear association between the systemic immune-inflammatory index and body mass index, and the inflection point was found to be 729.3. Conclusions The systemic immune-inflammatory index is positively associated with body mass index among adults in the United States and has the potential to enhance efforts to prevent adult obesity.