Combined Effect of Body Mass Index and Waist Circumference in Predicting Nonalcoholic Fatty Liver Disease

Background: Body mass index (BMI) and waist circumference (WC) are the most widely used anthropometric indices for identifying obesity. This study aimed to compare and clarify the usefulness of BMI, WC, and the combination of these two indicators in predicting nonalcoholic fatty liver disease (NAFLD). Methods: This cross-sectional study included 15,267 Korean adults. We defined four obesity categories using BMI and WC as follows: BMI nonobese and WC nonobese (BNWN); BMI obese and WC nonobese (BOWN); BMI nonobese and WC obese (BNWO); and BMI obese and WC obese (BOWO). Analysis of variance was used to compare fatty liver severity across each category. The odds ratios (ORs) and 95% confidence intervals (CIs) for NAFLD were calculated using multiple logistic regression. Results: Compared with BNWN, participants with BNWO were 3.235 (95% CI: 2.774-3.773) times more likely and participants with BOWN were 2.344 (95% CI: 2.045-2.687) times more likely to have NAFLD. Participants with BNWO had higher OR for NAFLD than those with BOWN. Moreover, BOWO participants had the highest OR of 4.788 (95% CI: 4.350-5.270) for NAFLD among all obesity categories. Conclusion: Combined obesity classification by BOWO is the most reliable indicator for NAFLD presence in Korean adults.