GPT and metabolic syndrome: Thus, we propose a working definition of NAFLD of: (i) results of liver imaging meet the diagnostic criteria of diffuse fatty liver that cannot be explained by any other causes; or (ii) an unexplained consistent increase in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and/or glutamyl transpeptidase (GGT) levels for at least 6 months in patients with any component of the metabolic syndrome.