Global burden of adult non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) has been steadily increasing over the past decades and is expected to persist in the future.

Background: At present, there is a dearth of comprehensive data at the global, national, and regional levels regarding the adult non-alcoholic fatty liver disease (NAFLD) prevalence. This cross-sectional study aims at ascertaining the prevalence of NAFLD and non-alcoholic steatohepatitis (NASH), utilizing body mass index (BMI) as a determining factor.

Methods: Based on the NHANES database, sigmoidal fitting curves were generated to establish the relationship between BMI and the risk of NAFLD/NASH. Utilizing BMI data from the NCD Risk Factor Collaboration (NCD-RisC) database at both global and regional levels, the prevalence of NAFLD/NASH among adults was estimated from 1975 to 2016, encompassing global, regional, and national perspectives. Additionally, projections were made to forecast the prevalence of adult NAFLD/NASH from 2017 to 2030.

Results: In 2016, the global prevalence of NAFLD was 41.12% for males and 37.32% for females, while the global prevalence of NASH was 15.79% for males and 16.48% for females. The prevalence of NAFLD/NASH increased with higher BMI in both genders. Over the period from 1975 to 2016, there has been a gradual increase in the global prevalence of NAFLD/NASH in adults, and this trend is expected to continue between 2017 and 2030. In males, the prevalence of adult NAFLD/NASH was found to be highest in High-income Western countries, while it was highest in Central Asia, Middle East, and North African countries after 1995.

Conclusions: The prevalence of adult NAFLD/NASH has been observed to increase annually, with significant variations in burden across different countries and regions.