Rational: The metabolic response to surgical trauma is enhanced by prolonged preoperative fasting, contributing to increased insulin resistance. This manifestation is more intense on the 1st and 2nd postoperative days and is directly proportional to the size of the operation. Aim: To compare whether preoperative fasting abbreviation and early postoperative refeeding associated with intraoperative and postoperative fluid restriction interfere in the evolution of patients undergoing gastrojejunal bypass. Methods: Eighty patients indicated for Roux-en-Y gastrojejunal bypass were selected. They were randomly divided into two groups: Ringer Lactate (RL) group, who underwent a 6 hours solids fasting, with the administration of 50 g of maltodextrin in 100 ml of mineral water 2 hours before the beginning of anesthesia; and Physiologic Solution (PS) group, who underwent a 12 hours solids and liquids fasting. Anesthesia was standardized for both groups. During the surgical procedure, 1500 ml of ringer lactate solution was administered in the RL and 2500 ml of physiological solution (0.9% sodium chloride) in the PS. In both groups, the occurrence of bronchoaspiration was analyzed during intubation, and the residual gastric volume was measured after opening the abdominal cavity. In the postoperative period in Group RL, patients started a liquid diet 24 hours after the end of the operative procedure; whilst for PS group, fasting was maintained for the first 24 hours, it was prescripted 2000 ml of physiological solution and a restricted liquid diet after 36 hours. Each patient underwent CPK, insulin, sodium, potassium, urea, creatinine, PaCO2, pH and bicarbonate dosage in the immediate postoperative period, and 48 hours later, the exams were repeated. Results: There were no episodes of bronchoaspiration and gastrojejunal fistulas in either group. In the analysis of the residual gastric volume of the PS and RL groups, the mean volumes were respectively 16.5 and 8.8, which shows statistical significance between the groups. In laboratory tests, there was no difference between groups in sodium; PS group showed a higher level of serum potassium (p=0.029); whilst RL group showed a higher urea and creatinine values; CPK values were even for both; PS group demonstrated a higher insulin level; pH was higher in PS group; sodium bicarbonate showed a significant difference at all times; PaCO2 values in RL group was higher than in PS. In the analysis of the incidence of nausea and flatus, no statistical significance was observed between the groups. Conclusions: The abbreviation of preoperative fasting and early postoperative refeeding of Roux-en-Y gastrojejunal bypass with the application of ERAS or ACERTO Project accelerated the patient’s recovery, reducing residual gastric volume and insulin level, and do not predispose to complications.