Abstract: The present invention relates to the field of gene therapy and, more particularly, to methods for the prevention and/or treatment of non-alcoholic fatty liver disease (NAFLD). The viral vectors disclosed in the present invention are preferably parvoviral vector, more preferably adeno-associated vectors (AAV) containing the gene encoding Sirtuin 1 (Sirt1) in the prevention and/or treatment of NAFLD. The present invention also discloses the pharmaceutical compositions comprising the viral vector and the method of prevention and/or treatment of NAFLD and related diseases by the administration of said pharmaceutical compositions.