Impact of body fat accumulation on metabolic dysfunction-associated fatty liver disease and nonalcoholic fatty liver disease in Japanese male young adults.

AIM: Nonalcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated fatty liver disease (MAFLD) are global concerns. The aim of this study was to reveal the relationship between body composition and NAFLD and MAFLD in male young adults. METHODS: We recruited 335 male graduate students from Gifu University who underwent a health checkup in April 2022. The diagnosis of NAFLD and MAFLD was based on health checkup data and ultrasonography. Muscle and fat mass were measured using bioelectrical impedance analysis and demonstrated as skeletal muscle mass index and fat mass index (FMI), respectively. We assessed factors associated with NAFLD and MAFLD using the logistic regression, decision tree, and random forest analyses. RESULTS: The median age of the participants was 22 years, and 9% were overweight or obese (body mass index ≥25 kg/m2 ), 8% had MAFLD, and 16% had NAFLD. In the multivariate logistic regression analysis, FMI was independently associated with NAFLD (odds ratio [OR], 1.49; 95% confidence interval [CI], 1.26-1.75; p < 0.001) and MAFLD (OR, 1.93; 95% CI, 1.51-2.46; p < 0.001). The decision tree and random forest analyses revealed that the strongest classifier for NAFLD and MAFLD was FMI. Additional analyses among nonobese individuals also showed the strong relationship between FMI, NAFLD, and MAFLD. CONCLUSION: Our study revealed that fat accumulation plays a key role in the development of NAFLD and MAFLD in male young adults, even in nonobese individuals. The results could shed new light on the pathophysiology of NAFLD and MAFLD in young adults.