Lean NAFLD is histologically less severe and tends to affect older patients

Abstract Objective: Nonalcoholic fatty liver disease (NAFLD) is related to obesity; little is known regarding NAFLD in lean individuals. This study aimed to determine pathological characteristics of lean NAFLD. Methods: The study enrolled biopsy-proven NAFLD patients from the Third People’s Hospital of Shenzhen from September 2017 to October 2021. Eighty-one patients were enrolled and classified into lean or obese groups by body mass index. Histology severity was assessed according to the steatosis-activity-fibrosis (SAF) score and was compared between lean and obese groups.Results: Among 81 patients, 12 (14.81%) were lean and 74 (91.36%) had nonalcoholic steatohepatitis (NASH). Lean NAFLD patients had less severe degree of activity (P=0.004) and fibrosis (P =0.047) and a lower proportion of NASH (P<0.001). No differences in steatosis (P=0.215) or advanced fibrosis (P=0.217) were observed. Lean NAFLD (43.83±10.28 vs 36.13±9.85 years, P<0.001) and NASH patients (46.29±12.83 vs 36.12±9.89 years, P=0.014) were older than obese NAFLD/NASH patients. The proportion of lean NAFLD/NASH patients in-creased with age. Compared with obese NAFLD patients, lean NAFLD patients had lower pro-portions of NASH (98.18% vs 42.86%, P<0.001) among patients aged <45 years and less severe fibrosis (P=0.046) among patients aged ≥45 years. No difference in steatosis/activity/fibrosis was observed between the two age groups (<45 years and ≥45 years) among lean NAFLD patients. Conclusion: In conclusion, fewer severe pathological changes were found in lean NAFLD patients. Histological progress was not significant between lean NAFLD patients aged <45 years and those aged ≥45 years.