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mobieusKnow Bariatric surgery explained: the four procedures and how each works History #868

Revision #868

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Patrick Bass
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Sep 5, 2026 4:30am
Summary
Editorial pass for house style across the knowledge base
'''Four operations do most of this work, and they change different things.''' Knowing which one you have had, or are considering, is what everything else in this section hangs off: the eating stages, the supplements, and what stays true for life.
== Sleeve gastrectomy ==
+ A large part of the stomach is removed, leaving a narrow tube. What is left holds much less and empties differently, and the part removed is involved in appetite signalling. Nothing is rerouted, so food takes its normal path.
− A large part of the stomach is removed, leaving a narrow tube. What is left holds much less and empties differently, and the part removed is involved in appetite signaling. Nothing is rerouted, so food takes its normal path.
'''What changes for good:''' a smaller capacity, a lifelong supplement schedule, protein first at every meal, and reflux as the thing most often reported afterwards.
== Roux-en-Y gastric bypass ==
A small pouch is made at the top of the stomach and joined directly to a section of small intestine, so food bypasses the rest of the stomach and the first part of the bowel. Capacity is smaller and less is absorbed.
Together, sleeve gastrectomy and gastric bypass account for approximately 90% of all operations performed worldwide (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).
'''What changes for good:''' a fuller supplement schedule because absorption is reduced, a join in the bowel that anti-inflammatory painkillers can damage, alcohol that reaches a higher peak more quickly, and dumping as a real possibility after sugary or fatty food.
== One-anastomosis gastric bypass ==
A long narrow stomach pouch is joined to a loop of small intestine with a single connection rather than two. The effect is similar to a Roux-en-Y bypass (less capacity and reduced absorption) with one join instead of two.
'''What changes for good''' is much the same as a Roux-en-Y bypass. Loopa treats it the same way for supplements and for the painkiller caution, which is the more protective of the two readings where published guidance does not name it separately.
== Duodenal switch and SADI-S ==
A sleeve is made, and then a much longer section of small intestine is bypassed than in a gastric bypass. SADI-S is a version with a single connection. These change absorption the most.
'''What changes for good:''' the largest supplement schedule of any of these procedures. The published guideline gives this procedure its own column, with 1,800–2,400 mg of calcium a day and higher amounts of the fat-soluble vitamins (Parrott J et al., ''Surgery for Obesity and Related Diseases'', 2017 · [https://doi.org/10.1016/j.soard.2016.12.018 doi:10.1016/j.soard.2016.12.018]).
== Adjustable gastric band ==
An inflatable band is placed around the top of the stomach and tightened or loosened through a port under the skin. Nothing is removed and nothing is rerouted, and it can be taken out. It is placed far less often now, and many people living with one had it fitted years ago.
'''What changes:''' a smaller supplement schedule than the other procedures, regular adjustments, and symptoms worth knowing. A band can slip or wear through the stomach wall.
== What the results look like ==
Durable weight loss after these operations is consistently reported at greater than 60% of excess weight, with variation depending on which operation was performed (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).
The published statement deliberately does not give a figure for each procedure, and neither do we. A number attached to an operation reads like a promise, and the range around any of them is wide. Your surgical team can tell you what they see in people like you, which is a more useful answer than an average.
== Related ==
* [[who-surgery-is-for|Who surgery is for]]
* [[the-staged-diet-after-surgery|The staged diet after surgery]]
* [[supplements-for-life|Supplements for life]]
== Where this comes from ==
+ Everything on this page is drawn from published clinical guidelines and peer-reviewed research, cited above. '''Loopa does not give medical advice.''' It does not decide whether a procedure is right for you, does not recommend one over another, and never sets a dose. Your care team does all three, and where they give you an instruction, theirs is the one to follow.
− Everything on this page is drawn from published clinical guidelines and peer-reviewed research, cited above. The full list, with a link to every original, is at [https://loopahealth.app/sources/ loopahealth.app/sources]. '''Loopa does not give medical advice.''' It does not decide whether a procedure is right for you, does not recommend one over another, and never sets a dose. Your care team does all three, and where they give you an instruction, theirs is the one to follow.

'''Four operations do most of this work, and they change different things.''' Knowing which one you have had, or are considering, is what everything else in this section hangs off: the eating stages, the supplements, and what stays true for life.

== Sleeve gastrectomy ==

A large part of the stomach is removed, leaving a narrow tube. What is left holds much less and empties differently, and the part removed is involved in appetite signalling. Nothing is rerouted, so food takes its normal path.

'''What changes for good:''' a smaller capacity, a lifelong supplement schedule, protein first at every meal, and reflux as the thing most often reported afterwards.

== Roux-en-Y gastric bypass ==

A small pouch is made at the top of the stomach and joined directly to a section of small intestine, so food bypasses the rest of the stomach and the first part of the bowel. Capacity is smaller and less is absorbed.

Together, sleeve gastrectomy and gastric bypass account for approximately 90% of all operations performed worldwide (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).

'''What changes for good:''' a fuller supplement schedule because absorption is reduced, a join in the bowel that anti-inflammatory painkillers can damage, alcohol that reaches a higher peak more quickly, and dumping as a real possibility after sugary or fatty food.

== One-anastomosis gastric bypass ==

A long narrow stomach pouch is joined to a loop of small intestine with a single connection rather than two. The effect is similar to a Roux-en-Y bypass (less capacity and reduced absorption) with one join instead of two.

'''What changes for good''' is much the same as a Roux-en-Y bypass. Loopa treats it the same way for supplements and for the painkiller caution, which is the more protective of the two readings where published guidance does not name it separately.

== Duodenal switch and SADI-S ==

A sleeve is made, and then a much longer section of small intestine is bypassed than in a gastric bypass. SADI-S is a version with a single connection. These change absorption the most.

'''What changes for good:''' the largest supplement schedule of any of these procedures. The published guideline gives this procedure its own column, with 1,800–2,400 mg of calcium a day and higher amounts of the fat-soluble vitamins (Parrott J et al., ''Surgery for Obesity and Related Diseases'', 2017 · [https://doi.org/10.1016/j.soard.2016.12.018 doi:10.1016/j.soard.2016.12.018]).

== Adjustable gastric band ==

An inflatable band is placed around the top of the stomach and tightened or loosened through a port under the skin. Nothing is removed and nothing is rerouted, and it can be taken out. It is placed far less often now, and many people living with one had it fitted years ago.

'''What changes:''' a smaller supplement schedule than the other procedures, regular adjustments, and symptoms worth knowing. A band can slip or wear through the stomach wall.

== What the results look like ==

Durable weight loss after these operations is consistently reported at greater than 60% of excess weight, with variation depending on which operation was performed (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).

The published statement deliberately does not give a figure for each procedure, and neither do we. A number attached to an operation reads like a promise, and the range around any of them is wide. Your surgical team can tell you what they see in people like you, which is a more useful answer than an average.

== Related ==

  • [[who-surgery-is-for|Who surgery is for]]
  • [[the-staged-diet-after-surgery|The staged diet after surgery]]
  • [[supplements-for-life|Supplements for life]]

== Where this comes from ==

Everything on this page is drawn from published clinical guidelines and peer-reviewed research, cited above. '''Loopa does not give medical advice.''' It does not decide whether a procedure is right for you, does not recommend one over another, and never sets a dose. Your care team does all three, and where they give you an instruction, theirs is the one to follow.

'''Four operations do most of this work, and they change different things.''' Knowing which one you have had, or are considering, is what everything else in this section hangs off: the eating stages, the supplements, and what stays true for life.

== Sleeve gastrectomy ==

A large part of the stomach is removed, leaving a narrow tube. What is left holds much less and empties differently, and the part removed is involved in appetite signalling. Nothing is rerouted, so food takes its normal path.

'''What changes for good:''' a smaller capacity, a lifelong supplement schedule, protein first at every meal, and reflux as the thing most often reported afterwards.

== Roux-en-Y gastric bypass ==

A small pouch is made at the top of the stomach and joined directly to a section of small intestine, so food bypasses the rest of the stomach and the first part of the bowel. Capacity is smaller and less is absorbed.

Together, sleeve gastrectomy and gastric bypass account for approximately 90% of all operations performed worldwide (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).

'''What changes for good:''' a fuller supplement schedule because absorption is reduced, a join in the bowel that anti-inflammatory painkillers can damage, alcohol that reaches a higher peak more quickly, and dumping as a real possibility after sugary or fatty food.

== One-anastomosis gastric bypass ==

A long narrow stomach pouch is joined to a loop of small intestine with a single connection rather than two. The effect is similar to a Roux-en-Y bypass (less capacity and reduced absorption) with one join instead of two.

'''What changes for good''' is much the same as a Roux-en-Y bypass. Loopa treats it the same way for supplements and for the painkiller caution, which is the more protective of the two readings where published guidance does not name it separately.

== Duodenal switch and SADI-S ==

A sleeve is made, and then a much longer section of small intestine is bypassed than in a gastric bypass. SADI-S is a version with a single connection. These change absorption the most.

'''What changes for good:''' the largest supplement schedule of any of these procedures. The published guideline gives this procedure its own column, with 1,800–2,400 mg of calcium a day and higher amounts of the fat-soluble vitamins (Parrott J et al., ''Surgery for Obesity and Related Diseases'', 2017 · [https://doi.org/10.1016/j.soard.2016.12.018 doi:10.1016/j.soard.2016.12.018]).

== Adjustable gastric band ==

An inflatable band is placed around the top of the stomach and tightened or loosened through a port under the skin. Nothing is removed and nothing is rerouted, and it can be taken out. It is placed far less often now, and many people living with one had it fitted years ago.

'''What changes:''' a smaller supplement schedule than the other procedures, regular adjustments, and symptoms worth knowing. A band can slip or wear through the stomach wall.

== What the results look like ==

Durable weight loss after these operations is consistently reported at greater than 60% of excess weight, with variation depending on which operation was performed (Eisenberg D et al., ''Obesity Surgery'', 2023 · [https://doi.org/10.1007/s11695-022-06332-1 doi:10.1007/s11695-022-06332-1]).

The published statement deliberately does not give a figure for each procedure, and neither do we. A number attached to an operation reads like a promise, and the range around any of them is wide. Your surgical team can tell you what they see in people like you, which is a more useful answer than an average.

== Related ==

* [[who-surgery-is-for|Who surgery is for]]
* [[the-staged-diet-after-surgery|The staged diet after surgery]]
* [[supplements-for-life|Supplements for life]]

== Where this comes from ==

Everything on this page is drawn from published clinical guidelines and peer-reviewed research, cited above. '''Loopa does not give medical advice.''' It does not decide whether a procedure is right for you, does not recommend one over another, and never sets a dose. Your care team does all three, and where they give you an instruction, theirs is the one to follow.