Surgery or GLP-1: no trial has ever compared them directly

What the drugs do in trials

In STEP 1, half the patients lose at least 15% of their weight. In SURMOUNT-1 at the highest dose, 57% lose at least 20%. These are considerable results, without precedent for an obesity drug.

What happens on stopping, and this is the decisive point

In SURMOUNT-4, 89.5% of those who continue keep at least 80% of their loss, against 16.6% of those who stop. These treatments work while they are taken. That is not a flaw, it is how they work, but it changes the comparison with a one-off operation.

What surgery does, at ten years

Two results are worth knowing before choosing. In SM-BOSS, 29.9% of sleeve patients were converted to bypass by ten years, against 5.5% the other way, for insufficient weight loss or reflux. And in SLEEVEPASS, remission of hypertension at ten years is 8% after sleeve against 24% after bypass.

The Swedish SOS cohort, following patients operated on between 1987 and 2001, shows loss stabilised at 25% at ten years after bypass, while unoperated controls vary by less than 2% across the whole period.

On mortality, the level of evidence is not the same

This asymmetry has to be stated plainly.

For semaglutide, the SELECT trial (NEJM, 2023) randomised 17,604 patients in secondary cardiovascular prevention and measures a 20% reduction in major cardiovascular events, 6.5% against 8.0%, hazard ratio 0.80 with an interval from 0.72 to 0.90. That is a randomised trial on an event endpoint.

For surgery, the data come from the SOS cohort, controlled but not randomised, with a median follow-up of 24 years: 22.8% deaths against 26.4%, hazard ratio 0.77 with an interval from 0.68 to 0.87, and a median life expectancy gain of 3.0 years. The follow-up is incomparably longer, but the design is weaker.

Matched comparisons between surgery and semaglutide give cardiovascular risk reductions of around 60%. That is far more than SOS measures, at 33%, and SELECT, at 20%. Such a gap fits residual bias better than a real effect, and we do not cite it as a measurement.

What the studies do not allow us to claim

That patients regain 80% of lost weight after stopping a GLP-1 has no primary source. The verified figures are two thirds regained in one year in the STEP 1 extension, across an exploratory subgroup of 327 patients, plus 14.0% over 52 weeks off treatment in SURMOUNT-4, and plus 6.9% over 48 weeks in STEP 4.

That the sleeve fails in 30% of cases has no source either. Three verified figures exist and measure three different things: 23.0% of patients lost less than half their excess weight at two years in the Swedish registry, 12.2% were reoperated at ten years in the French national database across 224,718 sleeves, and 29.9% were converted at ten years in SM-BOSS.

One caveat on SELECT: mean follow-up is 39.8 months, in patients who already have cardiovascular disease. The trial says nothing about primary prevention or the long term.

In practice, if this concerns you

Three questions structure the discussion. Are you considering lifelong treatment or a one-off procedure, since the withdrawal trials show the drug effect stops with the drug. Do your BMI and comorbidities match the trial populations, since SELECT enrolled patients with cardiovascular disease and a BMI of at least 27, and the surgical trials BMIs around 44. And if surgery is on the table, sleeve or bypass, since the ten-year conversion gap is 29.9% against 5.5%.

Noria Health arranges a full metabolic work-up near Brussels within 24 to 48 hours: nutritional and psychological assessment, full blood work, screening for comorbidities, upper endoscopy, and reflux assessment before any sleeve decision. The report is issued within 24 hours, follow-up is structured at D14, D30 and D90, and surgery is considered only around day 10 if it is needed.

What Noria Health does not do: present surgery and injectable treatments as two interchangeable options. They are two strategies with different levels of evidence, different horizons and different risks. Acute abdominal pain, persistent vomiting or collapse after bariatric surgery are matters for the emergency services in your country, immediately, not for an appointment.

Further reading

• Metabolic surgery, what the trials measure
• Colonoscopy: 19% fewer cancers
• Heart: 44% of people with hypertension do not know they have it

Sources

1. Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity, STEP 1. N Engl J Med, 2021;384:989-1002. https://pubmed.ncbi.nlm.nih.gov/33567185/
2. Wilding JPH, Batterham RL, Davies M, et al. Weight regain after withdrawal of semaglutide, STEP 1 extension. Diabetes Obes Metab, 2022;24:1553-1564. https://pubmed.ncbi.nlm.nih.gov/35441470/
3. Rubino D, Abrahamsson N, Davies M, et al. Effect of continued weekly semaglutide vs placebo on weight loss maintenance, STEP 4. JAMA, 2021;325:1414-1425. https://pubmed.ncbi.nlm.nih.gov/33755728/
4. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity, SURMOUNT-1. N Engl J Med, 2022;387:205-216. https://pubmed.ncbi.nlm.nih.gov/35658024/
5. Jastreboff AM, le Roux CW, Stefanski A, et al. Tirzepatide for obesity treatment and diabetes prevention. N Engl J Med, 2025;392:958-971. https://pubmed.ncbi.nlm.nih.gov/39536238/
6. Aronne LJ, Sattar N, Horn DB, et al. Continued treatment with tirzepatide for maintenance of weight reduction, SURMOUNT-4. JAMA, 2024;331:38-48. https://pubmed.ncbi.nlm.nih.gov/38078870/
7. Salminen P, Gronroos S, Helmio M, et al. Effect of laparoscopic sleeve gastrectomy vs Roux-en-Y gastric bypass on weight loss at 10 years, SLEEVEPASS. JAMA Surg, 2022;157:656-666. https://pubmed.ncbi.nlm.nih.gov/35731535/
8. Kraljevic M, Susstrunk J, Wolnerhanssen BK, et al. Sleeve gastrectomy versus Roux-en-Y gastric bypass at 10 years, SM-BOSS. JAMA Surg, 2025;160:369-377. https://pubmed.ncbi.nlm.nih.gov/39969869/
9. Wolnerhanssen BK, Peterli R, Hurme S, et al. Laparoscopic Roux-en-Y gastric bypass versus laparoscopic sleeve gastrectomy, merged data from two randomized trials. Br J Surg, 2021;108:49-57. https://pubmed.ncbi.nlm.nih.gov/33640917/
10. Brown A, et al. Comparative weight loss with GLP-1 receptor agonists and bariatric surgery. Obesity (Silver Spring), 2026;34:1583-1591. https://pubmed.ncbi.nlm.nih.gov/42345739/
11. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes, SELECT. N Engl J Med, 2023;389:2221-2232. https://pubmed.ncbi.nlm.nih.gov/37952131/
12. Ryan DH, Lingvay I, Deanfield J, et al. Long-term weight loss effects of semaglutide in obesity without diabetes, SELECT. Nat Med, 2024;30:2049-2057. https://pubmed.ncbi.nlm.nih.gov/38740993/
13. Sjostrom L, Narbro K, Sjostrom CD, et al. Effects of bariatric surgery on mortality in Swedish obese subjects. N Engl J Med, 2007;357:741-752. https://pubmed.ncbi.nlm.nih.gov/17715408/
14. Carlsson LMS, Sjoholm K, Jacobson P, et al. Life expectancy after bariatric surgery in the Swedish Obese Subjects study. N Engl J Med, 2020;383:1535-1543. https://pubmed.ncbi.nlm.nih.gov/33053284/
15. Axer S, Szabo E, Naslund I. Weight loss and remission after sleeve gastrectomy and gastric bypass, SOReg. Obes Surg, 2023;33:2973-2980. https://pubmed.ncbi.nlm.nih.gov/37587379/
16. Lazzati A, Bechet S, Jouma S, Paolino L, Jung C. Revision surgery after sleeve gastrectomy, a nationwide study. Surg Obes Relat Dis, 2020;16:1497-1504. https://pubmed.ncbi.nlm.nih.gov/32636173/

See also: all our articles on bariatric and metabolic surgery.

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