A Randomized Controlled Study Evaluating Bariatric Surgery as a Treatment for Severe NASH With Advanced Liver Fibrosis in Non-severe Obese Patients

Inclusion Criteria: * Provide written informed consent and agree to comply to the study protocol prior to enrolment. * BMI and Brunt Fibriosis score: * For F3 fibrosis patients: 35\>BMI≥ 30kg/m² ; Fibroscan ≥ 9kPa or FibrometreVM ≥0.526 predicting a F3 fibrosis score grade within 1 month before inclusion or F3 fibrosis score grade diagnosed by hepatic biopsy performed before inclusion. * For F4 fibrosis patients: 50\>BMI≥ 30kg/m² ; Fibroscan ≥ 15kPa predicting a F4 fibrosis score grade within 1 month before inclusion or F4 fibrosis score grade diagnosed by hepatic biopsy performed before inclusion. * Fibroscan ≥ 9kPa or FibrometreVM ≥0.526 predicting a F3 or F4 fibrosis score grade within 1 month before inclusion Or F3 or F4 fibrosis score grade diagnosed by hepatic biopsy performed before inclusion. * Patient should agree to have one liver biopsy during the screening period (before randomization, the randomization will be permitted after at least a second reading performed by pathologist of CHRU Lille to confirm the histological diagnosis of NASH with advanced fibrosis (F3-F4)) for the diagnosis purpose (if no histological biopsy within 1 month before inclusion is available) and one at the end of the treatment period for assessment of the treatment effects. * For patients with cirrhosis, patients must fulfil all the following criteria: Platelets \> 125 000, PT \> 80 %, Albumin \> 35 g/L, MELD score at inclusion \< 9, CPT score \< 6, No history of previous decompensatio…