FGF21 and metabolic dysfunction-associated steatotic liver disease: In this Japanese study, 12 weeks of physical exercise reduced CK18 and FGF21 levels in patients with NAFLD, despite no changes in the body mass index, indicating that the exercise-induced metabolic switch and proper metabolic flexibility is probably more related to the normalization of FGF-21 and CK-18 than simply a reduction in body weight.