Mitochondria regulate hepatic lipid metabolism and oxidative stress. Ultrastructural mitochondrial lesions, altered mitochondrial dynamics, decreased activity of respiratory chain complexes, and impaired ability to synthesize ATP are observed in liver tissues from patients with alcohol-associated and non-associated liver diseases. Increased lipogenesis with decreased fatty acid β-oxidation leads to the accumulation of triglycerides in hepatocytes, which, combined with increased levels of reactive oxygen species, contributes to insulin resistance in patients with steatohepatitis.