Key points
- The sleeve removes most of the stomach and turns it into a narrow tube. The intestine is not changed.
- It leads to substantial weight loss in many people, but results vary from one person to another.
- Its main drawback is acid reflux. It also requires vitamins and follow-up for life.
How the operation works
The surgeon removes most of the stomach, lengthways. What remains is a narrow tube, the “sleeve”; the path that food takes is not changed. The operation is done by laparoscopy (keyhole surgery), through small incisions. The part removed cannot be put back, but a sleeve can later be converted into a bypass if needed.
Concept and medical supervision: Dr Pierre Fournier
All steps as text
- Before surgery (0–3 s). This is the route food takes before a sleeve gastrectomy.
- Staple line (3–10 s). The outer part of the stomach is separated along a staple line.
- Part removed (10–19 s). It is removed, leaving a tube-shaped stomach.
- Route of food (19–25 s). Food still passes through the pylorus and into the intestine.
- Result (25–30 s). The digestive route is preserved.
Simplified diagram, not to scale.
What you can expect
The sleeve reduces the size of meals and also changes the hormones that regulate hunger and fullness1.
In the Swiss trial that compared it with the bypass over more than ten years, weight loss was close to that achieved with the bypass2. Results vary from one person to another, and weight regain remains possible (Weight regain).
Risks and constraints specific to the sleeve
The risks common to all obesity surgery are described on the page Benefits, risks and constraints. The sleeve has its own particular features:
- Acid reflux: this is the most important point. It can appear or get worse after the operation; it is monitored during follow-up, and an endoscopy may be offered2.
- Second operation: over the years, a second operation may be needed, most often because of reflux, usually by converting the sleeve into a bypass2.
- Leak (fistula) along the staple line: this can occur shortly after the operation and is one of the complications monitored in hospital3.
On the other hand, because the intestine is not changed, the sleeve does not carry the risk of internal hernia that is specific to the bypass, and the stomach remains accessible by gastroscopy3. Significant reflux or a hiatus hernia usually means another technique is preferred: see Choosing an operation.
Hospital stay and follow-up
The hospital stay usually lasts two to three nights. Getting back to eating and to your activities is supported by the team and adapted to your situation.
Vitamin and mineral supplements, regular blood tests and follow-up are needed for life, as after a bypass4. Life and follow-up after surgery
Frequently asked questions
I already have reflux: does that rule out the sleeve?
Not automatically, but it is a major factor in the choice. A gastroscopy is part of the assessment before the operation.
What happens if the sleeve is not enough?
After an assessment, conversion to a bypass is possible: this is revisional surgery, performed in a specialist referral centre1.
What next?
If this page sounds like your situation, you can book a surgical assessment consultation. Its purpose is to review your situation and the possible options; any operation is then decided collectively by the team, with you.
Your request is received by the Centre’s appointments team, who will organise the next steps with you. You do not need to check for yourself whether you meet the criteria.
Medical review of the French version: Dr Pierre Fournier
Scientific sources and references
Sources accessed on 12 October 2026. Reimbursement rules and information on medicines change over time.
- Swiss Society for the Study of Morbid Obesity and Metabolic Disorders (SMOB). Directives pour le traitement chirurgical de l’obésité, in force from 1 July 2023 (in French). View source
- Kraljevic M, Süsstrunk J, Wölnerhanssen BK, et al. Long-term outcomes of laparoscopic Roux-en-Y gastric bypass vs laparoscopic sleeve gastrectomy for obesity: the SM-BOSS randomized clinical trial. JAMA Surg. 2025;160(4):369-377. doi:10.1001/jamasurg.2024.7052. View source
- IFSO-EC, version adopted by the SMOB. La prise en charge en urgence du patient opéré de chirurgie métabolique et bariatrique (poster for emergency departments), 2026. View source
- Gerber PA, Collet TH, Favre L, et al. Swiss obesity clinical practice guidance. Swiss Med Wkly. 2026;156:5415. View source
- Author
- Prepared for the Centre from the sources cited
- References
- See “Scientific sources and references” on this page