The present invention relates to the use of a pharmaceutical composition in the form of extended-release tablets containing Pirfenidone for treating NAFLD / NASH and advanced liver fibrosis by decreased serum cholesterol and triglycerides as well as reducing the content of hepatic fat accumulation, both in the form of macrosteatosis and microsteatosis. Additionally, its use as an agonist for PPARgamma (peroxisome proliferation receptor activated gamma), PPARalpha (peroxisome proliferation receptor activated alpha), LXR and CPT1, key molecules in the metabolism of fatty degradation and inflammation of the liver. In addition, another use is the induction of decreased expression of NFkB master gene, transcriptional inducer of hepatic inflammatory process factor. All of these events results in the reversal of NAFLD / NASH and advanced liver fibrosis.
