Introduction:
Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is a common liver disease linked to metabolic dysfunction. While often associated with obesity, MASLD also affects lean individuals, raising questions about its underlying mechanisms and clinical implications.

Aim:
This paper aims to review the latest insights into MASLD, with a specific focus on lean individuals, exploring its prevalence, pathogenesis, cardiovascular risk and treatment strategies.

Material and methods:
A systematic review was conducted using PubMed and Google Scholar to examine recent studies on MASLD, particularly in lean patients. Key terms included ‘metabolic dysfunction-associated steatotic liver disease’ and ‘nonalcoholic fatty liver disease.’

Results and discussion:
Approximately 10%–20% of MASLD cases occur in lean individuals, who exhibit impaired glucose metabolism and visceral fat accumulation. Despite fewer metabolic comorbidities, lean MASLD patients show similar disease severity and poorer outcomes compared to obese patients. The condition is linked to insulin resistance, genetic factors, and alterations in the gut microbiome. Cardiovascular risk in lean MASLD patients is lower than in obese counterparts, but advanced age and hepatic fibrosis increase the likelihood of cardiovascular complications. Moreover, lean patients face higher overall mortality rates, with hepatocellular carcinoma more prevalent among them.

Conclusions:
Lean MASLD remains an under-recognized but significant condition. Early diagnosis, personalized treatment approaches, and further research are essential for improving outcomes. Future studies should focus on refining diagnostic tools, identifying biomarkers, and developing tailored therapies for lean patients.