How each one works
A gastric sleeve removes around 80% of the stomach, leaving a narrow tube. Less capacity, less hunger, no change to the route food takes. A gastric bypass leaves the stomach in place but creates a small pouch and connects it directly to a lower part of the small intestine, so food bypasses most of the stomach and the duodenum. That rerouting is what changes gut hormones — and it is the reason the two operations behave differently in patients with diabetes, even though they produce similar weight loss.
Side by side
| Gastric Sleeve | Gastric Bypass | |
|---|---|---|
| Average weight loss | ~40% of excess weight | ~40% of excess weight |
| Type 2 diabetes | Improves | Often preferred |
| Acid reflux | Can worsen it | Often improves it |
| Complexity | Simpler, shorter | More complex |
| Intestine rerouted | No | Yes |
| Reversible | No | Technically, rarely done |
| Supplements for life | Yes | Yes, stricter |
| From | from €1,800 | from €2,400 |
When surgeons lean towards the sleeve
It is the simpler operation, with a shorter operating time and no intestinal rerouting, which makes it the common starting point for patients without significant reflux or long-standing diabetes. It is also the usual choice where a patient has adhesions or other reasons that make intestinal surgery less attractive, and for younger patients, since it leaves the option of converting to a bypass later.
When surgeons lean towards the bypass
Two situations in particular: type 2 diabetes, where the hormonal change tends to improve blood sugar control more directly, and significant acid reflux or a hiatus hernia, which a sleeve can aggravate but a bypass often relieves. It is also the operation of choice for patients who have already had a sleeve and need a revision.
What does not decide it
Price should not. The gap between the two packages is small relative to the decision, and choosing the cheaper operation when your history points to the other one is a false economy. Nor should the idea that one “works better” — on weight loss alone, they are comparable. What should decide it is your medical history, your tests and your surgeon’s assessment.
Send us your height, weight and medical history on WhatsApp and we will tell you, free of charge, which of the two your case points towards — and why.
Frequently asked questions
Which one causes more weight loss?+
Neither, in the figures we stand behind: both the sleeve and the bypass lead to an average loss of around 40% of excess weight. Claims that the bypass always delivers much more weight loss are overstated. The difference between the two lies elsewhere — mainly in their effect on diabetes and reflux.
Which is better if I have type 2 diabetes?+
The bypass is often preferred where type 2 diabetes is present, because rerouting the intestine changes gut hormones in a way that tends to improve blood sugar control more directly. Your surgeon decides based on how long you have had diabetes and how it is currently managed.
Which is better if I have acid reflux?+
The bypass. A sleeve can make existing reflux worse in some patients, whereas a bypass often improves it. If you have significant reflux or a hiatus hernia, say so at consultation — it genuinely changes the recommendation.
Is the sleeve reversible?+
No. The sleeve permanently removes most of the stomach, so it cannot be undone, though it can be converted to a bypass later if needed. The bypass does not remove the stomach and is technically reversible, but reversal is a major operation and is rarely done.
Do I need vitamins for life with both?+
Supplementation and regular blood tests are part of the treatment for both, and more so after a bypass, which reduces absorption as well as capacity. If taking supplements daily for life is something you know you would not keep up with, tell your surgeon — it affects which operation is appropriate.
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