# Do GLP-1 Drugs Work After Bariatric Surgery? Two Randomized Trials Say Yes Two randomized trials tested GLP-1 drugs after bariatric surgery underdelivered. Semaglutide: -18.0% vs +0.4%. Liraglutide after gastric bypass: -8.8% vs +1.1%. Publisher: This GLP Editorial Team Canonical: https://thisglp.com/research/glp1-after-bariatric-surgery-evidence Updated: 2026-09-18 Published: 2026-09-17 [← Research](https://thisglp.com/research) Evidence # Do GLP-1 Drugs Work After Bariatric Surgery? Two Randomized Trials Say Yes Semaglutide took off 18.0% where placebo gained 0.4%; liraglutide took off 8.8% where placebo gained 1.1%. Both trials are small, and both untreated groups were still gaining. [This GLP Editorial Team](https://thisglp.com/about)September 20268 min readUpdated September 2026 Weight change after surgery had underdelivered · semaglutide, 68 weeks · -18% · its placebo arm · +0.4% · liraglutide, 56 weeks · -8.8% · its placebo arm · +1.1% · Both placebo arms gained. That is most of the gap. **Research, not medical advice.** This GLP is independent and educational. Nothing here is a substitute for individualized care from a licensed clinician, and reading it creates no doctor–patient relationship. Talk to your own provider before starting, stopping, or changing any medication, peptide, or therapy. See our [methodology](https://thisglp.com/methodology) and [terms](https://thisglp.com/terms). ## Key takeaways - Two randomized trials have tested a GLP-1 drug in people whose weight loss after bariatric surgery fell short, and both found a large effect. - Semaglutide 2.4 mg: weight fell 18.0% against a 0.4% gain on placebo over 68 weeks, an adjusted difference of 19.18 points (95% CI -23.4 to -14.8). - Liraglutide 3.0 mg after gastric bypass: 8.8% lost against a 1.1% gain, with 76% reaching at least 5% loss against 17% on placebo. - Both trials are small — 70 and 132 people — and both placebo arms gained weight, which is most of why the gaps look so wide. Yes, in both trials that have asked, and by a margin wide enough that the more interesting question is what the untreated group was doing. Surgery that has underdelivered is one of the few places in this field where somebody has actually run the randomized comparison, rather than looking back at records afterwards. ## The semaglutide trial A double-blind trial randomized 70 people whose weight loss after bariatric surgery had been suboptimal to semaglutide 2.4 mg or placebo, and followed them for 68 weeks [\[1\]](https://thisglp.com/research/glp1-after-bariatric-surgery-evidence#ref-1). Sixty-three were in the intention-to-treat sample, with 34 and 29 contributing data at the final visit. Weight fell 18.0% on semaglutide and rose 0.4% on placebo, an adjusted difference of 19.18 percentage points with an interval running from 23.4 to 14.8. Metabolic parameters and quality of life improved alongside it, measured with the kind of instrument this site examined in [the health utility analysis](https://thisglp.com/research/do-glp1-drugs-improve-quality-of-life). ## The liraglutide trial, in a narrower group An earlier randomized trial gave liraglutide 3.0 mg or placebo to people 18 to 120 months past a Roux-en-Y gastric bypass specifically, with lifestyle counseling for everyone, over 56 weeks [\[2\]](https://thisglp.com/research/glp1-after-bariatric-surgery-evidence#ref-2). Eighty-nine received the drug and 43 the placebo. Fifty-six weeks after a Roux-en-Y gastric bypass, 18 to 120 months post-operation. | | Liraglutide 3.0 mg | Placebo | | --- | --- | --- | | Total body weight change | −8.8% | +1.1% | | Lost at least 5% | 76% | 17% | | Lost at least 10% | 51% | none | | Lost at least 15% | 26% | none | | Went below their post-operative low | 21% | none | Fifty-six weeks after a Roux-en-Y gastric bypass, 18 to 120 months post-operation. Randomized, double-blind, placebo-controlled trial, 132 participants That last row is the one worth sitting with. A fifth of the people on liraglutide ended up below the lowest weight their operation had ever taken them to, and nobody on placebo did. ## What the pooled studies add A 2024 meta-analysis gathered eight studies and 557 people treated with a GLP-1 drug after bariatric surgery, from a search that took in trials and observational studies, and it went to press before the semaglutide trial above was published [\[3\]](https://thisglp.com/research/glp1-after-bariatric-surgery-evidence#ref-3). Against placebo, liraglutide took off 6.0 kg more over six months. Against liraglutide, semaglutide took off 2.57 percentage points more at six months and 4.15 points more at twelve. It also carried the cost that the headline figures leave out. On liraglutide, fat mass fell 4.78 kg, but lean mass fell 3.01 kg with it, and whole-body bone mineral density dropped slightly. The authors call bone and muscle a concern that still needs evaluating, and it is the same [body-composition question](https://thisglp.com/research/do-you-lose-muscle-on-a-glp1) that follows these drugs outside surgery too. ## Read the placebo arms before the headlines Untreated, both comparison groups gained The placebo arm gained 0.4% in one trial and 1.1% in the other, which is why the differences — 19.18 points and roughly ten — look so enormous next to what the drugs did on their own. This is not a trick; it is the natural history of weight regain after surgery, and it is the thing the operation was supposed to prevent. But a reader comparing 18.0% here against the 15% of a placebo-controlled obesity trial elsewhere is comparing against two different floors, which is the reasoning this site sets out in [the ladder of comparators](https://thisglp.com/research/tirzepatide-vs-real-clinical-practice). ## What these two trials do not establish They are small. Seventy people and 132 people, with 63 contributing to the analysis in one of them, is not the scale at which safety signals appear or subgroups separate. The semaglutide trial recorded eight serious adverse events and one suspected unexpected serious adverse reaction, which is what a trial that size can tell you about harm: very little. The liraglutide trial also lost a lot of people. Only 65% of the drug group and 53.4% of the placebo group completed, which the authors attribute to the pandemic. Serious adverse events occurred less often on liraglutide than on placebo. They also tested different drugs after different operations. One enrolled mixed bariatric procedures and the other only Roux-en-Y gastric bypass, so they are two answers to adjacent questions rather than a replication. Nobody has compared a GLP-1 drug against a revision operation, which is the choice a person in this position is actually weighing — and the broader surgery-against-drug comparison is in [surgery against a GLP-1 on cardiovascular outcomes](https://thisglp.com/research/bariatric-surgery-vs-glp1-cardiovascular). What the trials do support is narrow and useful: when an operation has underdelivered, adding one of these drugs moves weight substantially, and doing nothing does not hold the line. What happens if the drug is later stopped is a separate question, answered in [what happens when you stop tirzepatide](https://thisglp.com/research/what-happens-when-you-stop-tirzepatide). ## Frequently asked Do GLP-1 drugs work after bariatric surgery? In both randomized trials that have tested it, yes. Semaglutide produced 18.0% weight loss against a 0.4% gain on placebo, and liraglutide 8.8% against a 1.1% gain after gastric bypass. Can you get below the lowest weight your surgery reached? Some did. In the liraglutide trial, 21% of participants went below their post-operative nadir weight, and nobody on placebo did. Why are the differences so large? Partly because both placebo groups gained weight — 0.4% and 1.1%. The comparison is against continued regain, not against a stable weight. How strong is this evidence? Directionally consistent but small: 70 and 132 participants, with 63 analyzed in one trial. That is not a scale at which safety signals appear or subgroups separate. Does semaglutide work better than liraglutide after surgery? In a 2024 meta-analysis of eight studies and 557 people, semaglutide took off 2.57 percentage points more body weight than liraglutide at six months and 4.15 points more at twelve. Is a drug better than revision surgery? Nobody has compared them in a trial, which is the comparison a person in this position is actually weighing. ## Sources 1. \[1\] Stanley C, Mallik R, Hamid N, Jassil FC, Reuven V, Ruwona T (2026). Semaglutide versus placebo in individuals with poor weight loss after bariatric surgery: a double-blinded, randomized, placebo-controlled trial Nature Medicine. [PMID 42174253](https://pubmed.ncbi.nlm.nih.gov/42174253/) 2. \[2\] Lofton HF, Maranga G, Hold R, Fielding G, Youn H, Gujral A (2025). A randomized, double-blind, placebo-controlled trial of weight loss using liraglutide 3.0 mg for weight recurrence after Roux-en-Y gastric bypass Surgery for Obesity and Related Diseases. [PMID 39401933](https://pubmed.ncbi.nlm.nih.gov/39401933/) 3. \[3\] Dutta D, et al. (2024). Glucagon-Like Peptide-1 Receptor Agonists in Post-bariatric Surgery Patients: A Systematic Review and Meta-analysis Obesity Surgery. [PMID 38502519](https://pubmed.ncbi.nlm.nih.gov/38502519/) ## Where to get it ### Best GLP-1 injections Every injectable seller we can verify, with the price each one publishes and an honest read of what the trials measured. [Compare providers →](https://thisglp.com/best/compounded-semaglutide) ## More in Evidence - [ 150 minutes · Weekly activity goal · 2 days · Muscle strengthening · Adapt · Symptoms and ability ### Exercise on Ozempic: Building Strength Without Ignoring Symptoms ](https://thisglp.com/research/exercise-on-ozempic) - [ STEP 1, semaglutide 2.4 mg vs placebo, % change at 68 weeks · LDL cholesterol · −2.5% vs +1.3% · Total cholesterol · −3.3% vs +0.1% · HDL cholesterol · +5.2% vs +1.4% · Triglycerides · −21.9% vs −7.3% · Wegovy label, Table 13. Adults without diabetes. Ozempic doses are lower. ### Does Ozempic Lower Cholesterol? What the Lipid Results in the Trials Show ](https://thisglp.com/research/does-ozempic-lower-cholesterol) - [ Where the insulin reduction came from, units per day · week 4 · 13.4 total · week 26 · 21.9 · the drug itself · the weight loss · The drug’s own contribution barely moved: 11.1 then 11.4. · Everything added between weeks 4 and 26 came from weight. ### Does Semaglutide Help Type 1 Diabetes? What Two Small Trials Found ](https://thisglp.com/research/semaglutide-in-type-1-diabetes)