Abstract
BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is a common liver condition affecting 25%-40% of the worldwide population. NAFLD is traditionally related to obesity and metabolic disorders. NAFLD can also affect non-obese individuals, termed "lean NAFLD" (LN), who exhibit a paradoxical combination of physical leanness and metabolic obesity. Factors contributing to LN remain unclear, necessitating further research. This analysis aims to understand LN's prevalence and metabolic characteristics compared to obese NAFLD (ON) populations. METHODS: This meta-analysis searched various databases until August 1, 2023. Inclusion criteria involved observational studies comparing LN with overweight/obese NAFLD. Data extraction included baseline characteristics, disease occurrence, metabolic profile, and clinical parameters-statistical analysis employed calculating risk ratios (RR) and standard mean differences. RESULTS: Twenty-five studies were analyzed. LN is associated with lower prevalence in both NAFLD (RR 0.27, 95% confidence interval (CI) 0.14-0.52, p = <0.0001) and total (RR 0.27, 95% CI 0.15-0.51, p < 0.0001) population. LN had lower diabetes mellitus (RR 0.78, 95% CI 0.71-0.87, p < 0.00001), dyslipidemia (RR 0.87, 95% CI 0.79-0.95, p = 0.002), hypertension (RR 0.80, 95% CI 0.74-0.87, p < 0.00001), and metabolic syndrome (RR 0.45, 95% CI 0.31-0.64, p < 0.00001) compared to those with ON. The LN group's lipid profile, blood pressure, and other clinical parameters were favorable compared to ON. CONCLUSION: The prevalence of NAFLD among lean and non-lean individuals varies by region. Our analysis revealed that LN is associated with lower metabolic diseases, fasting blood sugar, blood pressure, and a more favorable lipid profile compared to ON.