Background Surgery induces insulin resistance that might be alleviated by a nutritional drink given preoperatively. The authors hypothesized that some of the beneficial effects of the drink could be attributed to the volume component (approximately 1 L) rather than to the nutrients. Methods Sixty patients scheduled for elective total hip replacement under spinal anesthesia were recruited to a clinical trial, and randomly allocated to preoperative fasting, to oral ingestion of tap water, or to oral ingestion of a carbohydrate drink. An intravenous glucose tolerance test calculated glucose clearance and insulin sensitivity on the day before surgery, in the postoperative ward, and on the day after surgery. Other parameters were stress (cortisol in plasma and urine), muscle catabolism (urinary 3-methylhistidine), and wellbeing. Results Fifty-seven patients completed the study. In the postoperative ward, the glucose clearance and the insulin response had decreased from the previous day by 23% and 36%, respectively. Insulin sensitivity did not decrease until the next morning (−48%) and was due to an increased insulin response (+51%). Cortisol excretion was highest on the day of surgery, while 3-methylhistidine increased 1 day later. Follow-up on the third postoperative day showed an average of 1.5 complications per patient. Wellbeing was better 2 weeks after than before the surgery. None of the measured parameters differed significantly between the study groups. Conclusions Preoperative ingestion of tap water or a nutritional drink had no statistically significant effect on glucose clearance, insulin sensitivity, postoperative complications, or wellbeing in patients undergoing elective hip surgery. / <p>Funding Agencies|Olle Engkvist Byggmastare Foundation||Stockholm County Council|2009-0433|</p>