Prevalence of Obesity in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Non-alcoholic fatty liver disease (NAFLD) has become more common in recent years. NAFLD is thought to be the primary cause of chronic liver disorders, and it has grown to be a significant global public health concern.

The prevalence of NAFLD has been steadily rising due to changes in lifestyle and dietary patterns, making it the most common chronic liver ailment globally.

The global prevalence of NAFLD is 30.1%. Recently published an international expert consensus statement about a new definition of metabolic dysfunction-associated fatty liver disease (MAFLD) to replace non-alcoholic fatty liver disease (NAFLD).

The new nomenclature of MAFLD is based on the presence of steatosis in \>5% of hepatocytes and the absence of excessive alcohol consumption or other causes of chronic liver disease, diagnosis of MAFLD could be established on the presence of hepatic steatosis in combination with one of the following three criteria: overweight/obesity; presence of type 2 diabetes mellitus; or evidence of metabolic dysregulation.

Metabolic dysregulation is defined as having at least 2 of the following metabolic risk abnormalities: high waist circumference, high blood pressure, high cholesterol, pre-diabetes, insulin resistance, and high plasma C-reactive protein levels.

In 2023, a new name, metabolic dysfunction-associated steatotic liver disease (MASLD). At the same time, experts introduced the broad umbrella term steatotic liver disease (SLD) to encompass both metabolic- and alcohol-based fatty liver disease. As an umbrella term, SLD allows for a continuum of alcohol ingestion to more adequately quantify its role in the progression of liver disease.

Irrespective of the nomenclature, MASLD is recognized as the most common cause of chronic liver disease (CLD), with the most recent meta-analysis suggesting that more than 38% of the world's adult population and between 7% and 14% of children are affected. Although the burden of MASLD is increasing around the world, in the many countries where viral hepatitis remains endemic, resources and efforts to treat and reduce that disease must continue to be prioritized.

Although NAFLD is observed predominantly in persons with obesity and/or type 2 diabetes mellitus (T2DM), an estimated 7%-20% oindividuals with NAFLD have leanbody habitus.

Lean NAFLD is generally defined by the presence of NAFLD in an individual who does not have an overweight or obese BMI. For adults, the Centers for Disease Control and Prevention and the World Health Organization define a normal range BMI to be between 18.5 and 24.9 kg/m2; BMI of 25-29.9 kg/m2 is considered overweight and BMI of 30- 34.9 kg/m2 is grade 1 obesity.

The World Health Organization recommends a lower BMI cutoff for overweight and obesity (BMI 23-27.5 kg/m2 for overweight and BMI \>27.5 kg/m2 for obesity) for those of Asian ancestry, recognizing that different populations may experience metabolic risk at a lower BMI. We suggest using the term lean NAFLD when discussing NAFLD in the setting of a normal range BMI.