Comparison of diagnostic value of abdominal obesity and metabolism-related indicators for non-alcoholic fatty liver disease in lean individuals

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease globally. The present study aims to investigate the diagnostic value of abdominal obesity and metabolism-related indicators for NAFLD in lean individuals. This cross-sectional study enrolled 894 participants diagnosed with fatty liver via ultrasound between July 2023 and July 2024. Patients with a body mass index (BMI) < 24 kg/m2 were defined as having “lean NAFLD”. Exclusion criteria included excessive alcohol consumption, viral hepatitis, and other conditions that may affect liver function. The normal control group comprised 1000 individuals with a BMI < 24 kg/m2 who underwent a normal physical examination during the same period. Basic characteristics and biochemical test results were compared between the two groups. Additionally, abdominal obesity and metabolism-related indicators were calculated, including the lipid accumulation product (LAP), waist-triglyceride index (WTI), body roundness index (BRI), waist-to-height ratio (WHtR), cardiometabolic index (CMI), triglyceride-glucose (TyG) index, and visceral adiposity index (VAI). We found that BMI, waist circumference, waist-hip ratio, fasting blood glucose, blood pressure and blood lipids in the group of lean NAFLD were higher than those of normal control group and statistically different (P < 0.001). Abdominal obesity and metabolism-related indexes were significantly higher than those of the control group (P < 0.001). The receiver operating characteristic (ROC) curves analyzed the diagnostic effect of the seven indexes for lean NAFLD, and found that LAP had the best effect (area under curve (AUC) = 0.889; 95% confidence interval (CI):0.874–0.903, sensitivity was 81.4%, specificity was 82.5%, and the Youden’s index was 0.639). Regression analysis after categorization based on cutoff values and adjusting for multiple confounders showed that LAP still had good risk prediction ability. The BMI < 24 kg/m2 population was stratified based on the presence of central obesity, and it was determined that LAP and BRI maintain their capacity to predict lean NAFLD in subjects with non-central obesity. Compared with other indicators, LAP has highest value in the diagnosis of NAFLD in normal BMI population, while BRI has some application value as a morphologic indicator. LAP and BRI still have diagnostic effect in people with normal BMI and non-central obesity.