Background: Ketosis after bariatric surgery is a metabolic process that occurs when the body breaks down fat for energy because of not getting enough carbohydrates. Insufficient production of ketone bodies reduces the rate of weight loss, and excessive amounts of ketones can lead to ketoacidosis or liver failure in patients with nonalcoholic steatohepatitis (NASH). The investigators hypothesize that weight loss is directly related to calorie intake, and a significant reduction in carbohydrate content leads to increased ketosis and the risk of ketoacidosis.

Objectives: The study aimed to compare the incidence of ketoacidosis and liver failure in patients with NASH with different intakes of carbohydrates in the early postoperative period after gastric bypass. In addition, the investigators want to find out how carbohydrate restriction will affect weight loss for up to 1 year.