Preoperative carbohydrate loading vs fasting: effects on postoperative recovery and outcomes in surgery

Abstract

Traditional preoperative fasting reduces aspiration risk but contributes to catabolism, insulin resistance and patient discomfort. Enhanced recovery after surgery (ERAS) protocols increasingly endorses preoperative carbohydrate loading (PCL) as an alternative. This systematic review, conducted according to PRISMA guidelines, evaluated randomized controlled trials (RCTs) published between 2020–2025 comparing PCL versus standard fasting in adult general surgery populations. Eligible studies included abdominal, colorectal and bariatric procedures. Data extraction covered trial design, carbohydrate regimens, recovery endpoints (time to gastrointestinal function, oral intake, ambulation, hospital stay), metabolic markers, complications and patient-reported outcomes. Six RCTs (sample sizes 63–240) met criteria. PCL was consistently safe, with no evidence of delayed gastric emptying or aspiration. Across trials, PCL improved patient comfort (reductions in hunger, thirst, fatigue, anxiety), attenuated insulin resistance and dampened inflammatory stress responses. Several studies demonstrated earlier gastrointestinal recovery and reduced hospital stay, though findings were inconsistent. Complication rates were lower in some cohorts, particularly colorectal surgery, but unchanged in others. In diabetic patients, PCL with individualized insulin protocols was safe and improved perioperative comfort, though bowel recovery was unaffected. Integration of PCL with other ERAS components, such as goal-directed fluid therapy, appeared to amplify benefits. In summary, PCL is a safe, well-tolerated alternative to prolonged fasting in general surgery. It consistently improves comfort and metabolic outcomes, while effects on length of stay and complications remain variable. Evidence supports incorporating PCL as part of multimodal ERAS pathways, with further research warranted in high-risk subgroups such as elderly and diabetic patients.