Clinical Factors Associated with Non-Obese Nonalcoholic Fatty Liver Disease Detected among US Adults in the NHANES 2017–2018

NAFLD can occur in non-obese individuals with BMI < 25 kg/m². Our goal was to examine the prevalence and clinical factors associated with non-obese NAFLD using vibration-controlled transient elastography (VCTE) with controlled attenuation parameter which estimates steatosis and fibrosis among US adults. We aggregated data from the 2017–2018 cycle of NHANES and included adults (age ≥ 20 years) with BMI < 25 kg/m² with complete data for the survey, medical examination, and VCTE along with controlled attenuation parameter (CAP). We excluded participants with risks of other liver diseases. We considered patients to have non-obese NAFLD if CAP was >285 dB/m, or non-obese NAFLD fibrosis if this CAP criteria was met and liver stiffness was >8.6 kPa. We calculated the adjusted OR and 95% CI for associations with non-obese NAFLD using multivariable logistic regression. The prevalence of non-obese NAFLD was 6.2% and Asian Americans (12.2%) had the highest non-obese NAFLD prevalence. Clinical factors associated with non-obese NAFLD were advanced age and metabolic syndrome (OR_adjusted = 6.8, 95% CI 3.0–15.5). In a separate model, we found elevated glucose (OR_adjusted = 4.1, 95% CI 2.1–7.9), triglycerides (OR_adjusted = 3.8, 95% CI 1.7–8.5), and truncal fat (100-unit increase OR_adjusted = 1.07, 95% CI: 1.04–1.10) were associated with higher odds of non-obese NAFLD. Meanwhile, low physical activity (OR_adjusted = 2.9, 95% CI 1.2–7.1) was also positively associated with non-obese NAFLD. Non-obese NAFLD is prevalent in the US and is highly associated with metabolic conditions and syndrome. Our results support the importance of considering racial/ethnic differences when investigating NAFLD in a clinical setting.