Transient Elastography of the Liver ( Fibroscan ) and Bariatric Surgery

Inclusion Criteria: * Subjects 18-65 years old * BMI \> 40 kg/m² or BMI \> 35 kg/m² with comorbidities * Willingness to take a metformin once a day for 6 months * Ultrasound diagnosed NAFLD patients * Reading and speaking Hebrew Exclusion Criteria: * Subject with mental illness or cognitive deterioration * Use of probiotic/antibiotic 3 mounts before surgery * Use of other antibiotic for more than 1 week during the study * Drug addiction * Excessive alcohol consumption (≥ 30 g/day in men or ≥ 20 g/day in women) * Treatment with drugs known to cause hepatic steatosis or elevation of liver enzymes (e.g. Corticosteroids, HAART, Amiodarone, high dose estrogens) * Treatment with drugs or supplements that may improve hepatic steatosis or liver enzymes (Vitamin E, Milk thistle, ω-3 fatty acid, Ursodeoxycholic acid) 3 months prior to the initiation of the study * Other causes of chronic liver disease ( e.g. viral hepatitis: HBV/HCV +, autoimmune hepatitis, Hemochromatosis, Wilson's disease) * Diabetic patients who are treated with antidiabetic medications, except diabetic patients who are treated for at least 6 months exclusively with Metformin at a stable dose * Subjects who began a new lipid reduction medications less than 6 months prior to the initiation of the study * Subjects with chronic conditions that could interfere with our study: active cancer, organ transplant subjects, advanced kidney or liver disease, inflammatory bowel disease and other systemic inflammatory conditions * Bariatric surgery in the past