Bariatric Surgery: Gastric Bypass vs. The Sleeve
About 250,000 people in the US get bariatric surgery each year. Worldwide the figure is north of 550,000. Most people have heard about bariatric surgery, but not many people know how it works. Even fewer know that the success of bariatric surgery (it does work!) is as much due to altering the hunger-hormone ecosystem as it is due to the physical shrinking of the stomach itself (the size of the stomach and the pathway food takes is inextricably linked to our hormones). Crazy right?
Before diving into bariatric surgery I want to address the disease of obesity generally and talk a little about what makes us hungry - this will provide some useful context.
Many people incorrectly think that obesity is caused by a lack of self discipline.
“All people need to do is exercise more, eat less, it’s all about calories in and calories out”.
This belief is incredibly widespread even among the medical community, and it is completely wrong.
While it is obviously true that [calories in] vs. [calories out] has a lot to do with weight, there is an embedded assumption in the belief above - that all calories are made equal.
There are three primary sources of calories and we call them the macronutrients: carbohydrates, fat & protein. We are now able to verify using neural imaging that carbohydrates are unique among the three macronutrients in that they actually cause an increased amount of blood flow to our brain’s reward centers. Even more importantly, a connection has been discovered between insulin sensitivity and brain response. Here’s a brief excerpt from a previous post we published called “Carbohydrate User Disorder?”
The pancreas of people living with type 2 diabetes still produces insulin, but their bodies don’t respond as strongly to it as they should. This is called insulin resistance, and the body’s default response to insulin resistance is to produce more insulin.
With that in mind, here’s the key quote from the study: “Those with higher insulin secretion after a glucose load had a lower activity level in the reward region compared to those who had lower insulin secretion”.
This means that people with lower insulin sensitivity are literally building up a tolerance for carbohydrates. Their body is providing less reward per calorie of carbohydrates than the bodies of people who have higher (healthier) insulin sensitivity.
This is analogous to the reward deficit model of addiction, which explains why those with addiction need to take increasingly large doses to get the same amount of pleasure.
It gets worse though. In addition to carbohydrates being addictive, they also stimulate our appetite and make us want to eat larger quantities in a single setting, and then make us hungry sooner - this is because they do not provide the same amount of satiety (a feeling of fullness) per calorie as fat and protein.
When a person starts putting on excess weight the body’s hunger-hormone ecosystem also starts to change. Hunger hormones are produced in the stomach and in the top part of the small intestine (and other places, hormones are suuuuuper complicated and we’re still learning). These hormones tell us when we should feel full, and the quantity and duration with which they are produced impacts how much our body wants to eat and how long it wants to pause between meals. This entire system breaks down with obesity, and in many cases people living with obesity will actually start producing more hunger hormones when they start eating.
We’ll finish off this introduction with the definition of “Obesity” from the The Obesity Medicine Association: “a chronic, relapsing, multifactorial, neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences.”
A bit more complex than calories in/calories out eh?
Now on to bariatric surgery
Bariatric surgery is actually quite fascinating, and we’ve got some graphics below that will make it easy to understand.
There are three main types of bariatric surgery.
Roux-en-Y (roo-en-wy) gastric bypass;
Sleeve gastrectomy;
Duodenal Switch procedures
In this post we’re only going to address the first two surgeries, both of which have less surgical risk and fewer side effects related to subsequent malnutrition and vitamin deficiencies. Much of the information in this post comes from this excellent overview provided by Dr. John Pilcher on his Youtube channel (linked here). Dr. Pilcher runs a very successful bariatric surgery practice in San Antonio, Texas.
Before diving into the differences between the two surgeries let’s talk about what’s similar.
First, these surgeries do work, and for many people they are life changing. It is common for patients to lose 30-50% of their excess body weight (the amount of weight above what would be considered medically healthy) within the first six months, and up to 75% of their excess body weight within a year.
Here’s a link to the University of Iowa’s Patient Center where they talk at length about the benefits. The below excerpt lists just some of the obesity-related medical conditions bariatric surgery is known to address:
Back pain
Sleep apnea
High blood pressure
Diabetes
Depression
GERD
The Obesity Medicine Association states that 90% of medical problems related to obesity will either improve or resolve after surgery, and According to The New England Journal of Medicine, an analysis known as the Swedish Obesity Study found that patients who underwent weight loss surgery had a 29% lower death rate when follow-up was conducted an average of 10.9 years later. Even better, a subsequent analysis saw a 41% reduction in all-cause long-term mortality.
These results are nothing short of miraculous, but they don’t mean surgery is for everyone. Bariatric surgery is usually recommended only for people who have tried medication and lifestyle changes under a physician guided medical weight loss program - and it still wasn’t enough.
With both surgeries, patients will need to supplement vitamins every day for the rest of their lives. Further, these surgeries are not panaceas where you get to go back to eating whatever you wanted. Patients will still need to restrict their carbohydrate intake (more below). However, once a person has had the surgery their body’s hunger hormone production drops. In most cases this reduces a desire for food generally but specifically it helps to do away with food cravings - which are usually for carbohydrate-based foods.
Both surgeries are performed laparoscopically (non-invasively). Small incisions are made and then the surgery is completed with cameras and surgical tools that can fit through those incisions. Surgery usually takes from a little less to a little more than an hour, and 90% of patients go home the same day or only spend one night in the hospital. The vast majority of people can go back to work after 2 weeks, and the main symptom they are likely to experience during those first two weeks is lethargy.
Gastric Bypass & The Sleeve
In a gastric bypass the majority of your stomach is separated from a tiny pouch that can hold about an ounce of food. For comparison, the average stomach before surgery can hold about 32 ounces.
The tiny pouch is connected directly to your small intestine, which had previously connected to your stomach through the duodenum. The duodenum is connected to a part of the small intestine lower down so that digestive juices still have a path to get through.
If you are worrying about whether your stomach will “stay in place” after surgery, don’t! The graphic has been simplified, but in reality there are many blood vessels connected to the stomach that bring it nutrients and oxygen, and they keep it secured firmly in place.
Gastric bypass surgery is reversible, but unlike with gastric bypass, during a sleeve surgery a portion of your stomach is actually removed, and hence the surgery is irreversible. That said, weight gain after reversal is likely, and physicians usually only recommend a reversal if there have been serious side effects from the initial surgery (not common).
Conceptually, a sleeve gastrectomy is simpler, though in practice this difference is far smaller than the graphic makes it seem and should not be considered a reason to select one surgery over the other. During a sleeve gastrectomy about 80% of the stomach is removed. The remaining portion of stomach is about the same size as a banana. As you can see there is no need to re-route parts of the small intestine.
Pros and Cons of each procedure
Gastric bypass has been around longer.
Gastric Bypass surgery has been around since the 80s. This means that the medical community has had plenty of time to do follow up studies for decades after patients have undergone the surgery. We’ve known for a long time now that gastric bypass usually results in an additional 10% weight loss within the first couple of years, but we’re now learning that the weight loss advantage tends to grow with time vs. the Sleeve. Sleeve surgery has only been around since 2005, so it isn’t until recently that the first 15 year follow up studies have started to be published. This is also an argument for gastric bypass surgery being better for younger patients, because it’s been around long enough that we know there won’t be any complications that arrive even many decades in the future.
3-5% of female patients do not get the hormonal benefits from sleeve surgery
We were unable to find a medical study to support this claim, but it comes directly from Dr. Pilcher’s experience with his own clinic and we thought it was worth sharing considering he has performed thousands of surgeries personally and their practice far more than that.
The claim is that older female patients with multiple medical conditions, particularly those with minimal muscle mass, sometimes don’t get the same hormonal benefits from Sleeve surgery as with gastric bypass. Remember this surgery works not only by shrinking the stomach, but also by changing our body’s hormone system that makes us want to eat in the first place. For 3-5% of female patients this hormonal change just doesn’t seem to happen. In these patients weight loss usually hovers around 30-40 pounds, but most people undergoing bariatric surgery are trying to lose far more weight.
Diabetes recurrence more likely with sleeve surgery
While both surgeries reliably put diabetes into remission for most patients after about a year, there is a high correlation between diabetes remission and weight. Because sleeve surgery is seeing greater amount of weight regain there’s an assumption that diabetes recurrence rates will be higher.
Reflux much better after gastric bypass vs. the sleeve
Gastric bypass surgery reliably makes reflux better, in many cases putting it into remission for the rest of the patient's life. Sleeve surgery frequently makes reflux worse, and can induce it in patients who didn’t have it previously. A study from 2021 found that up to 40% of people who had sleeve surgery developed GERD afterwards. Interestingly, for between 2% and 5% of patients who get sleeve surgery, the reflux is bad enough that they need to go back and get gastric bypass surgery.
Data also show that 8-10% of sleeve patients end up having sufficient trauma in their esophagus from reflux and heartburn that they qualify as having something called Barrett’s esophagus - not good. Because of this, it is now commonly recommended that patients who get sleeve surgery have an endoscopy done every 5 years to monitor potential damage.
The sleeve ain’t all bad
It probably feels like we’ve been ragging on the sleeve a lot. There are definite situations where the sleeve is the way to go. Tobacco use can cause bad ulcers after gastric bypass, so can the use of NSAIDs like aspirin. For any patient who expects to return to using tobacco after the surgery (you usually have to quit for the month leading up to it) or who expects to take NSAIDs - the sleeve is better.
Dumping Syndrome - a condition in which food, especially food high in sugar, moves from your stomach into your small bowel too quickly after you eat - is far more likely to occur with gastric bypass than the sleeve. Dumping syndrome symptoms include nausea, loose bowels, diarrhea, flushing, lightheadedness, a rapid heart rate and cramping.
Worth pointing out, sometimes people consider this a feature rather than a bug. It is very rare to get dumping syndrome unless you eat a lot of sugar: a big piece of cake, drinking lots of fruit juice, eating a large bowl of rice, etc. These are things that most people should be limiting anyway.
The last thing we’ll say about the sleeve is that it is better for patients who have major ongoing health problems related to things like chemotherapy, organ transplants, heart bypass, etc. Sleeve surgery is less likely to interfere with these types of health problems. Also, because sleeve surgery is performed only in the upper abdomen and doesn’t require working with the small intestine, it is the better choice for people who have already had major abdominal surgery.
Final thoughts
Surgery is a big deal, and it isn’t a way to avoid lifestyle changes. It will help reduce the temptation to eat (in the case of bypass particularly with respect to carbs due to Dumping Syndrome), but patients will still need to follow a lower carb diet, on top of supplementing vitamins daily for the rest of their lives.
Bariatric surgery should be considered only after trying (and not succeeding) to lose weight under a physician’s guidance during a full-blown medical weight loss program.
If nothing else works, the surgery is worth getting. It’s been around long enough that there is plenty of data that shows enormous benefits to quality of life, improvement across a range of chronic conditions, and extending both life and health span.