MASLD stands for metabolic dysfunction-associated steatotic liver disease. It describes a form of steatotic liver disease associated with cardiometabolic risk factors and is the term that has largely replaced non-alcoholic fatty liver disease (NAFLD).

Steatotic liver disease (SLD) is the overarching term for liver diseases characterised by an excessive accumulation of fat in hepatocytes. MASLD is the most common form. Metabolic dysfunction-associated steatohepatitis (MASH) is the progressive inflammatory form of MASLD and is characterised by hepatic steatosis, inflammation, and hepatocellular injury.

The SLD classification also includes MetALD, which refers to steatotic liver disease in individuals with metabolic dysfunction and alcohol consumption above the threshold defined for MASLD but below that generally associated with alcohol-related liver disease. Other categories include alcohol-related liver disease, SLD caused by specific factors such as medications, and cryptogenic SLD, in which no identifiable cause can be established.

The increasing prevalence of SLD is closely associated with the rising prevalence of obesity. More than 70% of people with obesity have steatotic liver disease. Approximately 43% have MASLD, and around 35% have MASH. Clinically significant liver fibrosis is present in approximately 20% of people with obesity and MASH.