Background and aim: Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD) affects up to 25% of the population and causes significant morbidity and mortality. Sarcopenia, the loss of muscle strength and quantity/quality, shares multiple pathways with MASLD, pointing to their possible association. In this systematic review, we aimed to describe the association between low muscle mass and/or strength and/or performance and the presence, development, or severity of MASLD/NAFLD. Methods: A search was performed in PubMed, Web of Science, Scopus, and LILACS, on 16 October 2020, for relevant studies, using a comprehensive search query and following PRISMA guidelines for systematic review conduction and reporting. Results: The search yielded 1042 results, of which 42 full papers and 11 poster abstracts were included. NAFLD was determined by imaging (n = 27), non-invasive tests (n = 13), liver biopsy (n = 11), or transient elastography (n = 2), and its severity by liver biopsy (n = 10), non-invasive tests (n = 7), transient elastography (n = 7), or imaging (n = 4). Muscle mass was, in most cases, adjusted for weight (n = 25), body mass index (BMI; n = 13), or height (n = 10). Most studies showed an association of low muscle mass and low strength with NAFLD presence and severity. However, the association of muscle mass with NAFLD was present when muscle mass was adjusted for weight or BMI but not when it was adjusted for height. A meta-analysis was not possible due to high heterogeneity in the methods of assessment of muscle parameters and NAFLD. Conclusions: This systematic review suggests the need for standardization of methods in this discipline. The issuing of specific guidance regarding sarcopenia in NAFLD would be of importance.
