 Study time schedule: At the time of the enrollment visit two visits are scheduled, the first before the beginning of the study and the last at the end. Surgery is scheduled no more than 7 days after the end of the treatment. At time of these two visits a clinical examination is performed avec calculation of the BMI, blood tests ASAT, ALAT; GGT, total, HDL and LDL cholesterol, triglycerides, glycemia, C-peptide, HbA1c, insulin, HOMA-IR, C reactive protein and a MRI to evaluate the volume and the fat content of the liver. At time of surgery duration of surgery and any eventual liver injury are recorded and a liver biopsy is performed. 