Background: Due to increases in obesity and type 2 diabetes, nonalcoholic fatty liver disease (NAFLD) is increasing. Current forecast models may not include non-obese NAFLD. We used a Bayesian approach forecasting the prevalence of NAFLD through 2040.Methods: Prevalence data from 245 articles involving 2,699,627 persons were used with a hierarchical Bayesian approach to forecast the prevalence of NAFLD through 2040. Subgroup analyses were conducted for age, gender, presence of metabolic syndrome, region, and smoking. Sensitivity analysis was conducted for clinical setting and study quality.Results: Forecasted 2040 prevalence rate was 55.7%, a 3-times increase since 1990 and 43.2% increase from the 2020 prevalence of 38.9%. The estimated average yearly increase since 2020 was 2.16%. For those aged <50 years and ≥50 years old, the 2040 prevalence rates were not different (56.7% vs 61.5%,
P=0.52).There was a significant difference in 2040 prevalence by sex (males-60% vs.50%, P+) but trend is stepper for females (2.5% vs 1.5%, P=0.025). No difference in trends overtime by region (P=0.48). The rate of increase was significantly higher in those without metabolic syndrome (3.8% vs. 0.84%, P=0.003) and for smokers (1.4% vs. 1.1%, P=0.011). There was no difference by clinical/community setting (P=0.491) or the quality of the studies (P=0.85) Conclusion: By 2040, over half the adult population is forecasted to have NAFLD. The largest increases occur in women, smokers and those without metabolic syndrome. Intensification of efforts raising awareness and determining long term solutions addressing driving factors of NAFLD are needed.