Normal-weight metabolic dysfunction-associated steatotic liver disease: reclassification, characteristics, and adverse liver outcomes across diverse populations

Abstract

Background/Aims: Previous studies have identified a substantial degree of agreement between the non-alcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated steatotic liver disease (MASLD) populations, but the same notion may not apply to normal-weight patients with a lower cardiometabolic risk burden. This study aims to investigate the cardiometabolic risk factor (CMRF) distributions between normal-weight and overweight/obese MASLD, the agreement between historical NAFLD and MASLD, and to compare the risk of liver-related events (LREs) and all-cause mortality in normal-weight versus overweight or obese MASLD. Methods: This study included participants with steatotic liver disease (SLD) from five cohorts in China (Hong Kong), South Korea, and the United States. Participants were recruited from settings including both hospitals and communities. Individuals were classified into normal-weight and overweight/obese groups. Results: This study included 33,793 participants with SLD from five cohorts, of whom 20,893 and 20,701 patients met the diagnosis of NAFLD and MASLD, respectively. Normal-weight patients with NAFLD demonstrated a lower CMRF distribution compared to those with overweight/obese NAFLD. In the community-based cohorts, the proportions with 0 CMRF ranged from 9.0 to 26.7% among normal-weight NAFLD patients, representing the discrepancy between MASLD and NAFLD definitions. Compared with the overweight/obese MASLD, the normal-weight MASLD had increased all-cause mortality (normal-weight vs. overweight/obese, 23.44 and 13.80 per 1,000 person-years; P<0.001) but not LREs (2.81 and 2.59 per 1,000 person-years; P=0.54) in the Hong Kong Clinical Data Analysis and Reporting System cohort. Conclusions: Normal-weight individuals with NAFLD demonstrated a lower distribution of CMRFs, resulting in the incomplete agreement between historical NAFLD and MASLD.