Key points
- When BMI is over 50, several treatments can be considered, including surgery, after a full assessment by the team.
- Your assessment, preparation and follow-up can be organised at the Centre, in Nyon; if your operation requires a specialist referral centre, we coordinate this step.
- Depending on your situation, medication and surgery can be combined or follow one another.
A full assessment, as a team
BMI is a marker, not a judgement: it does not sum up your health or your history. When it is over 50, the assessment looks in particular at breathing and sleep, the heart, diabetes, mobility and your quality of life, as well as nutrition and the support you need. See Understanding your BMI and looking beyond the number.
The choice of treatment is discussed with you and the multidisciplinary team. The decision is made collectively, taking into account your health, your expectations and your preferences.
Preparing for the operation
Preparation aims to make the operation safer: treating associated conditions, for example sleep apnoea or diabetes, moving within your abilities and receiving nutritional support. Starting to lose weight during the preparation can make the operation easier, in particular by reducing the size of the liver1. It is not a mandatory condition: this goal is discussed during your preparation.
See also Preparation and assessment before obesity surgery.
Surgical options
Several options can be discussed. No operation is chosen on the basis of BMI alone: the choice takes into account your health, your associated conditions, your preferences and the demands of follow-up.
- Sleeve gastrectomy or gastric bypass. These are the most commonly performed operations in Switzerland2. They can also be discussed when BMI is over 50.
- A two-stage procedure. A sleeve gastrectomy first, then, if needed, a second operation such as a gastric bypass or a duodenal switch, once health and weight have improved3.
- Duodenal switch or SADI-S. These operations reduce food absorption further and require lifelong nutritional follow-up and supplements4, 5. In Switzerland, the duodenal switch is performed in specialist referral centres and SADI-S only as part of a study3, 6.
These procedures are described in more detail on the page Other procedures and new approaches. The choice is made with you, weighing the expected benefits, the risks and the demands of follow-up: see also Choosing an operation.
Combining medication and surgery
Medication may be discussed before the operation, to support preparation, or afterwards, if your health goals call for it. It is neither compulsory nor a routine step: the decision is individualised7. See Medication and surgery: complementary approaches.
In Nyon, and when the operation must take place in a specialist referral centre
At the Centre
You can be welcomed and supported at the Centre in Nyon, including when your BMI is over 50. Your assessment, preparation and follow-up can be organised there. If your operation requires a specialist referral centre, we coordinate this step with the appropriate hospital. Wherever possible, and with the agreement of the host centre, Dr Pierre Fournier performs your operation there himself.
Depending on your situation, the appropriate hospital may be a specialist referral centre in Geneva (HUG), Lausanne or Neuchâtel.
Medical recommendation
In Switzerland, when BMI is over 50, the guidelines provide for the operation to be performed in a specialist referral centre. Hôpital de Nyon (GHOL) is recognised by the SMOB as a primary bariatric surgery centre: it performs basic procedures3, 8.
Before surgery can be considered, two years of weight management, on your own and/or with professional support, are needed. Follow-up at the Centre counts towards these two years: coming to the Centre does not reset the clock.
For reimbursement, basic health insurance requires that appropriate weight-loss treatment for two years has not been effective9, 3. The team checks with you that the treatments you have followed meet this condition; a personal effort is not automatically sufficient.
Long-term follow-up
After the operation, follow-up is lifelong, with nutritional support and regular check-ups: see Life and follow-up after obesity surgery.
Frequently asked questions
Do I need to lose weight before having surgery?
It is not compulsory. Losing weight can sometimes make the operation easier; the team tells you what is helpful in your situation.
Are the risks higher when BMI is very high?
When BMI is very high, the operation and the anaesthetic need particular care: the Swiss guidelines class them as higher-risk procedures3.
Before suggesting an operation, the team assesses in particular your breathing and sleep, your heart, any diabetes, your mobility and your general health. Preparation is then adapted to your situation: treatment of associated conditions, nutritional support, physical activity within your abilities and, in some cases, weight loss before the operation. The expected benefits and the risks are discussed with you.
Can I be followed up in Nyon if my operation takes place in a specialist referral centre?
Yes: your assessment, preparation and follow-up can be organised at the Centre. See In Nyon, and when the operation must take place in a specialist referral centre.
What next?
If this page sounds like your situation, you can book a surgical assessment consultation. It is an opportunity 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 15 October 2026. Reimbursement rules and information on medicines change over time.
- Stenberg E, Dos Reis Falcão LF, O’Kane M, et al. Guidelines for perioperative care in bariatric surgery: Enhanced Recovery After Surgery (ERAS) Society recommendations, a 2021 update. World J Surg. 2022;46(4):729-751. View source
- Gerber PA, Collet TH, Favre L, et al. Swiss obesity clinical practice guidance. Swiss Med Wkly. 2026;156:5415. View source
- 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
- Salminen P, Kow L, Aminian A, et al. IFSO consensus on definitions and clinical practice guidelines for obesity management: an international Delphi study. Obes Surg. 2024;34(1):30-42. View source
- Salte OBK, Olbers T, Risstad H, et al. Ten-year outcomes following Roux-en-Y gastric bypass vs duodenal switch for high body mass index: a randomized clinical trial. JAMA Netw Open. 2024;7(6):e2414340. View source
- SMOB. Surgical procedures: established procedures (basic and complex) and procedures not established in Switzerland (“in evaluation”), SMOB website page, undated, accessed on 15 October 2026. View source
- Cohen RV, Busetto L, Levinson R, et al. International consensus position statement on the role of obesity management medications in the context of metabolic bariatric surgery: expert guideline by the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO). Br J Surg. 2024;111(12):znae283. View source
- SMOB. List of recognised centres, as of 1 May 2026. View source
- Office fédéral de la santé publique (OFSP). Annexe 1 de l’ordonnance sur les prestations de l’assurance des soins (OPAS), edition of 1 July 2026: chapters 1.1 and 2.1. View source
- Author
- Prepared for the Centre from the sources cited
- References
- See “Scientific sources and references” on this page