Prolonged fasting may increase the organic response to trauma. Carbohydrate-based drinks have been tested and they may reduce insulin resistance. No study so far has aimed to examine the possible benefits of whey protein drink in the composition of preoperative drinks.

The patients will be randomized into two groups: the carbohydrate-protein group (CHO-P) and the control group (CO). The patients will reeive a specific drink to their group on the evening prior to surgery and three hours before the operation. The CHO-P group will receive 474 ml (evening drink) or 237 ml (3h prior to operation drink) of a solution containing 14% whey protein (100% lactoalbumin), 86% carbohydrates (45% hydrolyzed corn starch and 55% sucrose) and 0% lipids (Resource® Breeze - Nestlé, São Paulo, Brasil) and the CO group will receive the same volume of water.

Outcome measures On the day of the surgery and on the first postoperative day blood samples will be collected for glucose, insulin, triglycerides, albumin, pre-albumin, CRP, and α-1-acid glycoprotein (α-1-GA) assays. HOMA-IR will be calculated

Inclusion Criteria:

• Adults (18-65 years-old)
• Both sexes
• Candidates to elective moderate operations such as open cholecystectomy, laparoscopic cholecystectomy and unilateral repair of inguinal hernia).

Exclusion Criteria:

• Acute cholecystitis
• Diabetes mellitus
• Chronic kidney failure
• Chronic liver disease ot serum bilirubin greater than 2 mg/dL, body mass index (BMI) above 35Kg/m2
• American Anesthesiologists Association (ASA) score above 2
• Gastro-esophageal reflux
• Gastroparesis or intestinal obstruction
• Patients with any non-compliance with the study protocol, or who had associated operations, or presented significant intraoperative occurrences, or experienced prolonged operations (lasting more than 3 hours) were also excluded.