Aim: To compare prospectively two bariatric surgery techniques: sleeve gastrectomy (SG) vs gastric bypass (GB) in the evolution of nonalcoholic fatty liver disease (NAFLD) measured by the transient elastography in the first year. Methods: This is a randomized clinical trial with morbidly obese patients, between 18-60 years old from a Federal Hospital, Ministry of Health, Brazil. Patients were divided into 2 groups: group 1 - SG (n = 30) and group 2 - GB (n = 30). The randomization was made by lots. In the GB the investigators created 30 ml pouch, with a pancreatic and an alimentary limb of 1 meter, and a calibrated gastroenterostomy (1.5 cm diameter). In SG the investigators calibrated the gastric tube with a bougie number 32 (70 ml). The variables were compared one week before surgery and in the postoperative time (1, 3, 6 and 12 months). The variables were: patient anthropometry, laboratory tests and the transient liver elastography.

Inclusion Criteria:

The eligibility criteria was:

• morbid obesity patient grade II or grade III (BMI > 35) in prepare to bariatric surgery.

Exclusion Criteria:

The exclusion criteria were:

• age under 18 years or greater than 65 years old,
• chronic diseases (heart failure, chronic liver disease), and
• alcohol abuse (abuse was considered in those who consume more than 14 drinks per week).