GLP-1 After Bariatric Surgery: Phase 4 Trial Now Recruiting

What is the GLP-1 after bariatric surgery trial testing?

The trial, registered on ClinicalTrials.gov as NCT06132477 and sponsored by the University of Missouri-Columbia, randomizes people undergoing bariatric surgery to either continue or discontinue their GLP-1 receptor agonist therapy. According to the registry record, it is a Phase 4 study with a planned enrollment of 150 participants, and its status was listed as recruiting when the entry was updated on September 10, 2026.

Phase 4 means the drugs involved are already approved and in routine use; the question is not whether they work but how they should be used in a specific clinical situation. The registry description says the trial will compare changes in weight and metabolic determinants between the two groups, which is the outcome that matters most to patients who arrive at surgery already on a GLP-1 medication.

GLP-1 receptor agonists mimic glucagon-like peptide-1, a gut hormone released after eating. The registry entry describes GLP-1 as a hormone that helps regulate blood glucose through improved insulin sensitivity and insulin release from the pancreas, controls hunger and induces satiety. The class includes semaglutide, marketed as Ozempic and Wegovy, alongside the dual GIP/GLP-1 agonist tirzepatide, sold as Mounjaro and Zepbound.

Why continuing or stopping after surgery is still an open question

Bariatric surgery and GLP-1 medications both produce weight loss, and both do it partly through the same biology. The trial record notes that bariatric procedures work not only by restricting calories but through changes in gut hormones, circulating bile acids and the gut microflora, as well as mechanisms that remain undefined. That overlap is exactly what makes the combination hard to predict.

One plausible outcome is additive benefit: surgery resets the hormonal environment and the medication sustains the effect, reducing the weight regain that a substantial share of surgical patients experience over the years that follow. The opposite is also plausible — that surgery already maximizes the relevant signalling and continued drug therapy adds cost, side effects and appetite suppression on top of an already restricted intake.

The registry entry is blunt about the state of the evidence, stating that the combined benefits of GLP-1 receptor agonists with bariatric surgery have only been studied to a limited effect. Most of what clinicians currently rely on comes from observational series and single-center experience rather than randomized comparison, which is what these trials are designed to supply.

If your protocol is built around semaglutide, our semaglutide dosage calculator can help you keep the arithmetic straight when a schedule is interrupted and later resumed.

According to the ClinicalTrials.gov registry entry, the Phase 4 study is sponsored by the University of Missouri-Columbia, plans to enroll 150 participants, and was listed as recruiting when updated on September 10, 2026.

GRABS: a second trial publishes its design

Running in parallel, the GLP-1 Receptor Agonists Post-Bariatric Surgery trial — abbreviated GRABS — has published its rationale, design and baseline characteristics in the journal Diabetes, Obesity & Metabolism, with Samuels JM, Williams CR, Patel MB and colleagues listed as authors. A design-and-baseline paper is not a results paper: it describes how the trial was constructed and who enrolled, and it is published before anyone knows the answer.

These papers matter more than they look. They lock in the primary outcome, the comparison groups and the analysis plan in advance, which makes it harder for a disappointing result to be reframed after the fact. For readers, they also signal roughly when results should be expected and what question the trial will and will not be able to answer.

Two independent randomized trials asking a version of the same question is a meaningful development for a field that has run largely on clinical judgement. If both report in the same direction, guidance for patients who reach surgery already on a GLP-1 medication becomes considerably firmer than it is today.

For the dual GIP/GLP-1 agonist, the tirzepatide dosage calculator covers the same ground.

The published GRABS design paper in Diabetes, Obesity & Metabolism sets out the trial's rationale, design and baseline characteristics ahead of any outcome reporting. the published GRABS design paper.

The wider perioperative question around GLP-1 medications

Continuation after surgery is a separate issue from what happens on the day of the operation. Because GLP-1 receptor agonists slow gastric emptying, anesthesiologists have spent the past two years working through whether treated patients carry additional aspiration risk under sedation, and professional societies have issued guidance on holding doses before procedures.

That work is continuing in the literature. A study by Albanese, Tomaselli, Berkane and colleagues in Aesthetic Plastic Surgery examined anesthetic safety and perioperative outcomes in GLP-1 receptor agonist-treated patients undergoing lipoabdominoplasty — a different operation, but the same underlying concern about how these drugs interact with anesthesia and recovery.

The distinction is worth holding onto. Guidance about pausing before an operation says nothing about whether therapy should resume afterwards, and vice versa. The Missouri trial and GRABS are aimed squarely at the second question, and both are decisions made with a surgical and prescribing team rather than independently.

Consistent side-effect logging across a surgical pause gives your care team a record they can actually read rather than a recollection.

Separately, a study of anesthetic safety in GLP-1-treated surgical patients undergoing lipoabdominoplasty was published in Aesthetic Plastic Surgery, reflecting continued attention to how these medications interact with anesthesia.

What we still do not know

Neither trial has published outcomes, so nothing here establishes that continuing or stopping a GLP-1 medication after bariatric surgery is better. The Missouri study is listed as recruiting, which means enrollment is not complete, and the GRABS publication covers design and baseline characteristics rather than findings.

Several things will remain unresolved even when results arrive. A 150-participant trial can detect differences in weight and common metabolic measures but is unlikely to resolve rarer safety questions. Neither registry entry, as summarized in the available records, specifies how findings would generalize across the different GLP-1 and dual-agonist medications now in use, or across the different surgical procedures patients receive.

There is also the practical matter of access. A patient whose insurance coverage for a GLP-1 medication ends at the point of surgery faces a different decision than one whose coverage continues, and randomized evidence does not change coverage policy on its own.

A pause and restart also complicates inventory tracking, since supply bought on one schedule may sit unused while the schedule changes.