We report the case of a 46-year-old man who achieved remarkable improvement of characteristic non-alcoholic steatohepatitis by dieting. Initially, his body mass index was 40.7kg/m(2). He proactively commenced a low calorie diet and his body mass index decreased to 28kg/m(2) after 4years. During the same period, we carried out liver biopsy four times. Liver fibrosis as well as inflammation, steatosis and ballooning improved, and the non-alcoholic fatty liver disease activity score decreased from 4 to 0. The fat deposits of liver tissue changed from macrovesicular droplets to microvesicular, and finally disappeared. Along with improved histology, alanine aminotransferase, homeostasis model assessment-insulin resistance, ferritin, leptin, high-sensitivity C-reactive protein and cytokeratin18 decreased, and adiponectin increased linearly. However, no clear changes were observed in markers for Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA(+)M2BP), typeIV collagen 7S, procollageIII peptide and fibrosis-4 index along with dieting. This is the first study to report gradual improvement of liver histology during four liver biopsies and fibrosis markers in a patient with non-alcoholic steatohepatitis who achieved complete recovery solely by dieting.