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Gastric Bypass vs. Sleeve, a 2021 Update

The Gastric Bypass and the Gastric Sleeve have been the most popular bariatric operations in the U.S. and worldwide, for many years.  And while these both continue to be effective operations that help many patients achieve excellent health improvement, some new information has shifted my personal practice just a bit in the direction of Gastric Bypass.  Stay tuned to learn more!

Background & Disclaimers

  • The big decision is to decide when you’re ready for bariatric surgery. For the vast majority of patients, both the Gastric Bypass and the Sleeve will be effective for weight loss and improved health.
  • For most patients, these are both good options for intervention, so don’t feel like there is a “right” or “wrong” choice. I do a lot of both operations, and I see that both are useful approaches.
  • This should be a shared decision, between you as the patient and your surgeon.
    Patient – this is your tool, you’ve got to feel comfortable. Your “vibe” or “gravitation” does matter.
    But also, your surgeon will collaborate with you in the decision process.  Not only will they incorporate your medical background, but also the operative capabilities that they and their team will bring to the table.
  • The Gastric Bypass in this discussion is a standard Roux-en-Y Gastric Bypass. This does not encompass variations such as the mini-Gastric Bypass or the One-Anastomosis Gastric Bypass, or any other variations which create malabsorption.
  • This blog doesn’t discuss Duodenal Switch, which achieves more weight loss than either the Gastric Bypass or Sleeve by creating an intentional malabsorption factor. The Duodenal Switch has a different set of pros & cons.
  • The Lap-Band is clearly not a good choice.

I like to begin the comparison with the many characteristics that are the same for the Gastric Bypass and the Sleeve.  Again, for most patients these are both good, effective operations.

  • Preparation is the same: education, liver shrinkage, insurance process
  • Both are minimally invasive (little incisions and a video camera)
  • Relatively quick surgery – a bit less than an hour for Sleeve and a bit more than an hour for Gastric Bypass
  • Same recovery and return to normal activity – home on the same day or next day, driving in 2-3 days, and feeling well by two weeks.
    (low stamina is common before the 2-week mark)
  • Same food plan: clean & low carb.  Both operations feature normal absorption of major nutrients like proteins and essential fats.
    Much has been posted about malabsorption with Gastric Bypass.  The standard Gastric Bypass that is discussed here has been shown to have normal absorption of macronutrients such as proteins and essential fats.  I’ve done a separate YouTube on this in case you want more information.
  • Same vitamins, daily for life. Both operations do reduce absorption of Iron and B12, to a similar degree.
  • We have the same experience with both operations that outcomes are better with long term follow up.

Obviously, there are some technical differences in how the surgery is done, and there are some differences in outcomes as well.  First, we’ll run through the anatomic differences in the surgical procedures and the different hormonal benefits that each surgery has, then we’ll touch on different outcomes.

Sleeve Gastrectomy


  • Surgery all takes place on the stomach
  • Remove large greater curve section, leaving small lesser curve section, about the size and shape of a small banana

The Sleeve promotes weight loss on two levels.  Of course, there is a smaller stomach and smaller food capacity, but there’s a LOT more to the weight loss equation.

To understand the positive hormonal impact of the Sleeve, we need to understand the obesity condition is NOT just a matter of eating too much food.  For most people, that’s not even the main issue.  The underlying problem, and one that must be corrected in order to achieve lasting weight loss, is that for people with the obesity disease the energy hormones and the fat management system are out of balance.  Research shows that there is a powerful fat management system (because a little bit of fat is a survival resource), and that (for a variety of reasons that are still being researched, probably different reasons for different people) the individual’s energy system believes that they need this excess stored fat for survival.  So, the body (functioning on a powerful unconscious level) fights to hold onto the excess weight even though we know intellectually that the excess weight puts strain on the body and damages health.

This is the ‘Set Point’ theory of obesity, and the only way to achieve lasting weight loss is to change the body’s energy hormone balance or ‘Set Point.’  The great news is that both the Gastric Bypass and the Sleeve are effective in lowering the fat storage Set Point.

In the case of the Sleeve, the hormone improvement comes in part from the fact that some hunger hormones (such as Ghrelin) are made only in the greater curve section of the stomach that’s removed.  So, there’s a cool sense in which we are taking out part of the troublesome hunger mechanism.  In reality, there is probably much more going on hormonally but this description fits very well with the typical patient experience where, yes, one can hold less food, but more importantly, one wants less food in a way that lasts over many years.

Gastric Bypass


The Gastric Bypass is also done with small incisions and the TV camera

  • One key part of the surgery happens in the upper abdomen. We separate the stomach into a tiny upper segment or “pouch,” and a lower segment that no longer receives food.  Momentarily, there’s no place for food to go, but don’t worry there is a plan!
  • Another key part of the operation happens in the mid abdomen, where we free up a section of small intestine (technically “jejunum”) and we bring it to the upper abdomen where we attach it onto the stomach pouch to serve as the new food pathway.
  • So when the surgery is complete, the food follows the new path directly into the small intestine and it bypasses the lower stomach as well as the duodenum (that will be important in a moment), while digestive juices are still produced by their respective organs and follow their path downstream to the bottom of the “Y,” where the connection facilitates mixing of food with digestive juice, and normal absorption going downstream.
  • Nothing is removed
  • Bypassed stomach is ok, intact blood supply
  • Nothing is done to the colon, this is shaded simply as a tool the artist used to show the small intestinal surgery more clearly. Both run a bit toward constipated.

You can see there’s a really small stomach so that patients hold less food, but I promised there would be a hormonal effect for the gastric bypass, right?  And, as you can see we’re not removing that large section of stomach as we do in the Sleeve, so where does the hormone effect come from?  Well it’s kind of complicated, and probably in real life it’s a lot more complicated than this outline, but if this is too much for you then you’re welcome to jump forward and just trust that patients feel a lot less hungry over time.

For those of you who are still with us, we’re going to outline roughly what’s called the “foregut theory” of weight loss after Gastric Bypass.  This theory says that in normal non-surgical anatomy, the duodenum is an important segment of the intestine to help the body assess food and to properly utilize food.  The inner lining of the duodenum is populated with special cells that notice food (type, amount, etc) then they network with surrounding organs (liver, pancreas, etc) through neuro-hormonal reflex pathways to (theoretically) help the body respond in real time to put food to work.

BUT, in the context of the obesity disease, this system can mis-react or over-react to food so that the body does not feel satisfied or “sated” from food, but instead can create a physical desire for more food.  This does not happen to everyone, but it’s a common experience in my patients and it may happen on an unconscious (still powerful) level even if it’s not something that you’ve noticed before.

When food takes the new pathway after the Gastric Bypass, this duodenal foregut system is taken “offline,” and other backup hunger systems take over so that the body has a more natural and more balanced hunger.  So here again, patients hold less food but more importantly they want less food in a way that lasts over time.

For you science and physiology nerds, we need to mention that the mechanisms we’re describing for Sleeve and for Gastric Bypass are probably just representations of a part of what’s going on.  The obesity hormone imbalance is probably not the same in everyone who has the obesity disease, so the interactions of surgery with individual hormone situations can be different.  Research has shown physiologic changes that appear to be useful but completely separate from what I’ve outlined here, including positive alterations in the colon microbiome and changes in the chemical composition of digestive juices following surgery.  Furthermore, much of the neuro-hormonal signaling is happening over a distance of just centimeters or millimeters; these functions will take many years for full elucidation.

There’s another important feature of this hormonal effect for weight loss, a feature that’s shared by both operations.  I’ve been telling you that the Obesity Disease shows up as an imbalance in the energy control system and the energy hormones, an unhealthy elevation of the set point for fat storage.  I’ve just now told you that both the Sleeve and the Gastric Bypass have a direct positive effect on that energy hormone balance, leading to a lower set point for fat storage.  It turns out that neither operation interferes with proper function of the nutrition control system, so that after Sleeve or Gastric Bypass patients do have hunger that shows up in support of the body’s actual nutritional needs.  This means that patients burn a lot of their excess fat but they do not become malnourished and they tend to lose an amount of weight that’s appropriate for their starting point.  To say it a different way, both operations cause patients to lose excess weight but not to lose healthy weight, whether they start at 400 pounds or just 185 pounds.

Interlude – Band marketing distortions

Now, you should have a good idea about the Gastric Bypass and the Sleeve in terms of  1) how they are done, and 2) how they work.

There’s still a lot of comparing and contrasting we should do, but first let’s invest a minute talking about why the web conveys an impression of Gastric Bypass that is so intense or “invasive” compared to the Sleeve.  It’s true that the Gastric Bypass has more complexity than the Sleeve, and that some parts of it are more technically challenging for the surgeon, but surprisingly the data show that the Gastric Bypass has very similar risk and physiologic impact compared to the Sleeve.  And yet, there is pervasive information on the web describing the Gastric Bypass as having a high complication rate and lots of nutrition problems.  Where does this mismatch come from?

I think that a lot of the distorted information comes from Band marketing.  The story is that the Lap-Band® was approved for use in the U.S. in 2001.  At that time the primary competition in the bariatric surgery space was the Gastric Bypass, because the Sleeve did not come along until 2005.  Of course, the Band had a manufacturer, and the manufacturer had a marketing campaign.  The “educational” piece of that marketing campaign selected key medical data to make the Band look good, and the Band marketers used carefully selected surgical literature about the Gastric Bypass to make it look scary and risky.  In fact, there were literature reports from the 80’s and 90’s that showed high complication rates for the gastric bypass while the (open) surgical technique was being worked out and when surgeons didn’t understand how to prepare patients well for surgery, but these reports were pushed by the Band marketers as being a true/complete representation of the Gastric Bypass.  Ironically, even though the Band procedure is now understood to be a failure, the Band marketing lives on by means of its web presence.  Just take the web information with a grain of salt!

Now, back to a comparison between the Sleeve and the Gastric Bypass.  We’re going to compare these as well as I can in the current state of knowledge, with the understanding that information about these operations and about the obesity disease continues to develop and it’s likely we’ll be due for another update comparison in a few years!

In particular, new information is becoming available about medium- and long-term outcomes for the Sleeve, which started being performed in 2005.  For the Sleeve, we’re only now seeing solid data for 10-year outcomes and the story may continue to evolve until we have 20-year outcomes.  There has not been as much change for the gastric bypass, which has been performed since the early 80’s and which has well-understood long-term results.

Recall that many practical aspects of the operations are the same:

  • Both have a fairly short hospital stay and a fairly quick recovery
  • Same food plan for both, with normal absorption of major nutrients
  • Significantly reduced hunger, with sustained and substantial weight reduction for most patients
  • Strong positive impact on weight and related problems including:
    High blood pressure, cholesterol and heart disease
    Breathing issues including sleep apnea and asthma
    Improved joint pain and reduced body inflammation
    Reduced cancer risk
  • Amount of weight loss is appropriate to the amount that the patient needs to lose

Although many of the positive health outcomes are the same, there are some differences:

  • Weight – there is a modest advantage toward Gastric Bypass with more weight loss in the short term, and there seems to be a greater difference in the long term. There is some chance of weight regain for both operations, but this seems to be a larger effect for the Sleeve that we’re seeing as long-term trends become evident.
    Also, every once in a while, only in female patients, the Sleeve seems to ‘miss’ the hormone target.  These are patients who do everything the right way, but they lose only 30-40 pounds of weight.  In my practice this seems to happen to 3-5% of female patients (a bit less than 1 out of 20), and unfortunately our current level of science does not help us know which patients are susceptible.
  • DM – remission of diabetes correlates mostly with weight level, so there is a percentage advantage toward Gastric Bypass.
  • Reflux – this is a major differentiator. The Gastric Bypass makes reflux much better (often into full permanent remission) while the Sleeve usually makes reflux worse.

There are several expected differences that separate the Sleeve and the Gastric Bypass:

  • Tobacco use – it’s going to be very important to avoid any tobacco use for at least 30 days leading into either one of these operations, for optimal lung function and for minimizing the risk of leak. After healing, the Sleeve is fairly resistant to tobacco use but the Gastric Bypass is very sensitive in the sense that even small amounts of tobacco can cause ulcers at the upper anastomosis with pain, bleeding, and possibly perforation.  If there is any serious possibility that you may smoke after bariatric surgery, that would be a large factor in favor of Sleeve over Gastric Bypass.
  • Aspirin family medicines, often abbreviated “NSAIDs” such as ibuprofen, Aleve, Naprosyn – here again, we’ll want you to stop these meds a short time before either surgery because they increase bleeding risk. And here again, after healing the Sleeve is fairly tolerant of NSAIDs while the Gastric Bypass is highly in  Even a few doses of a medicine like ibuprofen can cause ulcers in Gastric Bypass, again with potential pain, bleeding, and perforation.
    We know that many patients use NSAIDs regularly due to various back and joint pains, or for headaches.  The good news is that weight loss will dramatically reduce those pains, and you’ll be much less likely to need NSAID meds.
    If you still need meds for this type of pain, we’re happy to prescribe Celebrex for our patients.  Celebrex has the same pain and anti-inflammatory benefits as classic NSAIDs, but has a MUCH lower ulcer risk.
  • Dumping Syndrome – this is a feeling of illness that comes after eating a large amount of sugars or after eating simple carbs. This reaction is mostly associated with Gastric Bypass, though it can happen to Sleeve patients too, especially with intake of sugars and carbs in the long run.
    The symptoms of Dumping Syndrome can include cramping abdominal pain, maybe vomiting, maybe diarrhea, then usually you feel weak and need to lay down for a while.  It feels pretty bad, but in general it’s not dangerous.
    In my experience, most Gastric Bypass patients have dumping only twice: once is when they test it ;),  and one other time when they unknowingly take in substantial sugars (a common cause is barbecue sauce).  Then in the long run, most Gastric Bypass patients tell me that they never experience dumping syndrome but they appreciate the potential for it, because that potential helps them stay on track with their food plan.

Moving from the expected or planned differences, we find both similarities and differences in the rate of complications and problems:

  • In bariatric surgery, there are three big complications that we watch out for in every single case. They can happen with either Gastric Bypass or Sleeve, and they are:  Leak, Bleed, and DVT/PE (blood clot that may form in the legs then float up to block blood flow in the lungs).  Fortunately, the three big complications are all very rare, and they are all in the category of “early” complications which means that (if, heaven forbid, one should occur) you’ll still be in the phase of close post-operative monitoring with us.
    Interestingly, and somewhat contrary to expectation, the rate for these rare-but-serious complications is the same for Gastric Bypass and for Sleeve.

Many people are surprised that the complication rates are so similar.  After all, doesn’t the Gastric Bypass look more complicated?  Actually, the Sleeve diagram is a bit misleading.  The artist’s conception is understandably simplified, and it looks quite simple to separate the stomach sections so we can extract that excess stomach.  The real stomach anatomy includes lots of blood vessels that supply oxygen and nutrients to the stomach, and that hold the stomach in place.  The stomach is also near the colon, the pancreas, and especially the spleen.  In our patients, the stomach is often covered with intrusive/mobile fatty tissue that can make it difficult to clarify these key structures.  Your surgeon needs to divide all those blood vessels and to carefully work around the nearby organs in order to accomplish the Sleeve.  Obviously this shouldn’t scare you about the Sleeve, and the data shows a very low complication rate, but the amount of surgical work is in the same ballpark as the gastric bypass.

  • Each of the operations has a significant complication that is (mostly) not shared with the other. For the Gastric Bypass, there is a very small risk of intestinal obstruction caused by scar tissue or internal hernia.  If this happens, repeat surgery is needed to straighten it out.  In most cases there is no long-term adverse impact but in rare cases there can be damage that requires removal of some intestine.
  • For Sleeve, in addition to the blood clot risk in the legs (same for both operations) there is a very small chance of a blood clot forming in the veins of the liver and the intestine. This blood clot can usually be treated with blood thinner but here again, it can be severe enough to cause intestinal damage and risk to life.
  • For both operations, there’s a small but realistic chance that you won’t make progress on handling oral fluid hydration as we normally expect. This can happen when all the surgical anatomy is appropriate and it can be just tissue irritation or a “glitch” in the healing process.  In this situation, about 2% of my Sleeve patients or about 3% of my Gastric Bypass patients need a week or two of IV fluids and vitamins that can be given nightly at home, then they are back on track.
  • Either of the operations has a small chance of requiring subsequent procedures such as endoscopy or even return to surgery, to fix something that’s not right on track. All these together run at less than 5%, and the early problems or glitches are a bit more likely with Gastric Bypass over Sleeve.
  • The complication that we’ve been learning the most about recently, because it takes some years to become fully apparent, is the tendency of the Sleeve toward Reflux and Heartburn. Many Sleeve patients find a need for increased meds to treat these symptoms, and for a few the symptoms are so bad that they need to come back for revision to Gastric Bypass (which treats reflux).
    A report came out in the summer of 2020, which actually showed that in some Sleeve patients there was enough inflammation of the esophagus caused by reflux of these caustic digestive juices to cause an injury pattern called Barrett’s esophagus.
    The new recommendation coming from these findings is that all Sleeve patients ought to have upper endoscopy done every 5 years to check on the esophagus and to ensure there is no injury that requires additional treatment.

On balance, these are both very safe and very effective operations.

The Gastric Bypass has a bit higher rate of needing IV fluids or corrective procedures in the short term, but it balances out with somewhat better weight loss and health benefits in the long run.

The Sleeve is also very effective for most patients, and it has the advantage when the patient is likely to be exposed to ulcer-creating substances (especially tobacco) in the future.

Here are some common patient factors that favor Sleeve:

  • Tobacco use
  • Expected need for NSAIDs
  • Extensive abdominal surgery in past
  • Continued illness, expected major medical interventions (such as heart operations, transplant surgery, cancer treatment)
  • (male)

Factors favoring Gastric Bypass

  • Reflux
  • Diabetes
  • A prior Lap-Band
  • Young – proven long-term results, all the parts are still there

Other Helpful Blogs:

Total Obesity Care

Taking Care of Your Gastric Pouch

Real Weight Goals