Diet is a modifiable key factor targeted in prevention and management of non-alcoholic fatty liver disease (NAFLD). The aim of the study is to investigate the effect of Mediterranean Diet (MedDiet) on clinical, biochemical and inflammatory profile in NAFLD patients with simple steatosis. Potential associations of single nucleotide polymorphisms to diet composition and patients' profile are investigated. In this non-randomised, open-label study, 44 untreated NAFLD patients with non significant fibrosis receive nutritional counsel to increase adherence to MedDiet. Adherence to MedDiet is estimated with MedDietScore. Furthermore, genotyping of STAT3 rs2293152 and GCKR rs1260326 single nucleotide polymorphisms takes place.