Preoperative Oral Carbohydrate Loading and Gastrointestinal Recovery After Bariatric Surgery in Metabolic Syndrome

This prospective, randomized trial aims to evaluate the efficacy and safety of preoperative oral carbohydrate loading for postoperative gastrointestinal recovery in patients with metabolic syndrome undergoing bariatric surgery. Eligible participants will be randomly assigned in a 1:1 ratio to either the preoperative oral carbohydrate loading group or the placebo group.

Participants in both groups will follow a standardized preoperative fasting protocol, with solid food prohibited for at least 6 hours before induction of anesthesia and clear liquids discontinued 2 hours before surgery. Participants in the POC group will consume 400 mL of an oral carbohydrate-containing beverage 2 hours before surgery, whereas participants in the control group will consume an equal volume of a placebo beverage with a similar appearance and taste but containing no carbohydrates at the same time point.

The primary outcome is postoperative gastrointestinal functional recovery, assessed using the GI-3 criteria. GI-3 recovery is defined as tolerance of oral intake accompanied by recovery of lower gastrointestinal function. The study will evaluate both the proportion of participants achieving GI-3 recovery within the predefined postoperative period and the time to GI-3 recovery.

Secondary outcomes include other measures related to postoperative gastrointestinal recovery, postoperative nausea and vomiting, quality of recovery, length of hospital stay, and other postoperative recovery-related outcomes. Perioperative blood glucose levels and glycemic variability will be assessed to evaluate the metabolic safety of preoperative oral carbohydrate loading.

Safety outcomes related to preoperative oral carbohydrate intake will also be assessed. Gastric ultrasonography will be performed before induction of anesthesia to evaluate gastric volume, corrected gastric volume, gastric antral cross-sectional area, and Perlas grade. The occurrence of perioperative regurgitation or pulmonary aspiration will also be recorded.

This study aims to determine whether, compared with placebo, preoperative oral carbohydrate loading can enhance postoperative gastrointestinal recovery in patients with metabolic syndrome undergoing bariatric surgery without increasing clinically significant perioperative glycemic fluctuations or aspiration-related risks.

Inclusion criteria

• adults aged 18-65 years;
• diagnosis of metabolic syndrome (≥3 of the following: elevated waist circumference, elevated triglycerides, elevated blood pressure, elevated fasting glucose, and reduced HDL-C);
• eligibility for bariatric surgery(body mass index ≥35 kg/m² or metabolic disease with body mass index 27.5-34.9 kg/m²), with planned Roux-en-Y gastric bypass or sleeve gastrectomy;
• provision of written informed consent and willingness to complete follow-up.

Exclusion criteria

• gastrointestinal motility disorders;
• severe cardiovascular, pulmonary, hepatic, or renal dysfunction;
• HbA1c ≥8.0%;
• fasting plasma glucose >10.0 mmol/L at the preoperative assessment;
• malnutrition;
• known allergy to carbohydrate preparations;
• pregnancy or lactation;
• previous bariatric or gastrointestinal surgery;
• chronic use of medications known to substantially affect gastrointestinal motility.