Patients with BMI 60 kg/m² or higher are the hardest operations in bariatric surgery. Thick abdominal wall, massive hepatomegaly, reduced working space, fragile fatty tissue, higher conversion and complication rates. Every bariatric surgeon knows this group. Almost no trial recruits it.
The standard answer is a short liver-reduction diet before surgery. It helps, but the effect is modest, hard to tolerate, and short-lived. GLP-1-based drugs now produce far larger and better-tolerated weight loss and are already being given before surgery in routine practice, without trial evidence. Retrospective series show more preoperative weight loss and no obvious harm, and no more than that (Obesity Research \& Clinical Practice 2026). A 2023 review of drugs on the surgical waiting list found that GLP-1 receptor agonists had never been evaluated for the preoperative indication at all.
Two registered trials are now adjacent to this question, and we cite both. The PreMO pilot randomizes 50 patients to open-label preoperative tirzepatide versus standard care, with tissue inflammation as the scientific focus (PMID 41643256; NCT06721507). A three-arm trial before one-anastomosis gastric bypass compares tirzepatide, ketogenic diet, and standard care, with weight loss at one year as primary (NCT07622992). Neither is blinded. Neither recruits BMI 60 and above. Neither measures whether the drug actually makes the operation easier and safer. The 2024 IFSO international consensus reached 100% agreement that evidence is insufficient to recommend routine preoperative medication, that use must be individualized, and that more research on benefits, risks, and outcomes is required; it also agreed, at 97%, that adequate protein and resistance exercise must accompany any preoperative drug treatment (PMID 39612579). This trial is the research that consensus calls for, and its preoperative program is built to the 97% requirement.
BMI 60 kg/m² or higher at first surgical assessment
Accepted by the multidisciplinary team for primary laparoscopic SG or RYGB
Able to self-inject and consent
Any previous bariatric or major upper abdominal surgery
GLP-1-based therapy within the previous 6 months
Type 1 diabetes
Pregnancy or conception planned within the study (obesity pharmacotherapy is stopped at least 2 months before any planned conception, per current labeling and the 2026 Standards)
Parallel
Semaglutide weekly injection
DrugWeeks 0 to 16: semaglutide 0.25, 0.5, 1.0, 1.7, then 2.4 mg weekly in 4-weekly steps, or matched placebo. Slower escalation allowed for tolerance; minimum acceptable plateau 1.7 mg. Last injection at least 7 days before surgery. Clear fluids for 24 hours before induction. Anesthesia manages every trial patient with full-stomach precautions. Surgery in weeks 17 to 18: laparoscopic SG or RYGB by the standardized unit technique, chosen and declared before randomization. Every operation recorded in full.
Placebo
DrugMatched placebo pens on the identical schedule
Mean operative difficulty score
Each anonymized video is rated independently by three blinded expert bariatric surgeons on five domains (liver size and handling; exposure; tissue fragility and adhesions; bleeding tendency; overall difficulty), each 1 to 5, total 5 to 25. The mean of the three raters is the patient's score. Raters are trained on a calibration set of 10 non-trial videos before unblinded rating begins; inter-rater reliability (ICC) is reported.
Preoperative percentage of total weight loss (%TWL)
Total weight loss measured in Kilograms
Operative time, skin to skin
From the start till the end of the surgery measured in minutes
Estimated blood loss
Bleeding intraoperative measured in milliliters
Intraoperative adverse events
Adverse intraoperative events (AIEs) occur in approximately 3% to 7% of bariatric surgeries and increase the relative risk of overall postoperative complications by about 90%. * Organ Injuries: Unintentional lacerations or punctures to the liver, spleen, stomach, intestines, or major blood vessels during trocar placement or dissection. * Intraoperative Bleeding: Significant hemorrhage from staple lines, mesentery, or the abdominal wall requiring intervention or transfusion. * Anastomosis and Staple Line Issues: Leaks, bleeding, or technical difficulties during the creation of pouches or connections (such as in a Roux-en-Y Gastric Bypass), identified via intraoperative leak tests. * Equipment Malfunction: Failures involving laparoscopic staplers, cameras, insufflation systems, or energy devices. * Anesthesia-Related Events: Severe hemodynamic instability, difficult airway management, or allergic reactions linked to medications.
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