Gastric bypass surgery: how it works, benefits & drawbacks

After endeavoring all other non-surgical options and not seeing sustainable results, weight-loss surgery might seem like the way to go. And that procedure can be gastric bypass surgery, one of the most demanded bariatric procedures.

Gastric bypass surgery can be a great option for high-risk overweight patients, and people who need help along the weight-loss journey. In this chapter, you will learn about what gastric bypass is, how it is performed, who is it performed by, what to weigh during consideration, and how the surgery is what it is today.

With this chapter, we plan to be your helping hand during your consideration and research. To decide on a life-changing procedure, every detail must be taken into account. So, let’s begin.

Gastric Bypass surgery

What is a gastric bypass?

Gastric bypass surgery is often a laparoscopic (minimally invasive) weight loss procedure for people over 40 BMI (body mass index). It still is considered an invasive procedure and there are set requirements for a bypass. That is why it is an inpatient procedure. Meaning you will stay in the hospital for 1-4 days after the surgery. You will be discharged after your observations by the bariatric team.

The surgery usually takes 12 hours. Your stomach is divided, and your small intestine is attached to the upper part of the stomach (pouch). As a result of this procedure, your food intake will be way lessand calorie absorption will be decreased by 70%. So you can expect dramatic weight loss.

What is the expected weight loss?

With gastric bypass surgery, you can expect to lose over 70% of your excess weight. Of course, this happens in the span of 1-2 years.

As you recover and time goes on, the rapid weight loss will slow down a bit. And also you will come across bariatric plateaus. During a plateau, your weight loss will halt or pause. This occurrence is normal. Your weight loss will go back to its pace after a short while.

The metabolic benefits of gastric bypass

Metabolism after gastric bypass surgery changes dramatically as the size of your stomach is reduced and your intestines are rerouted. A hormone called GLP1 that’s produced in the stomach is responsible for appetite control and the function of the gastrointestinal tract. After the gastric bypass, the production of this hormone increases, indirectly causing a metabolism boost.

Gastric bypass surgery: procedure, expectations and types

In short, gastric bypass surgery itself consists of 2 steps. First, the stomach is divided into 2 parts: the upper part and a lower part. Secondly, a part of the intestine is rerouted and attached to the upper part of the stomach. 

Before you are sent to the operating room, the bariatric team performs a complete physical exam on you. After the exam, blood tests and an ultrasound of the gallbladder will take place. After the tests are cleared, you will be on your way to your surgery.

You will be sedated and before beginning the surgery, the surgeon will take a look at your stomach via endoscopy to address if there are any issues present that can affect the surgery and to determine the actions they are going to take. After it has been planned, your surgery begins.

Preparations: First, the surgeon will make 3-4 incisions on your abdominal wall. Using these incisions, trochars will be placed and your abdomen will be inflated. After that, all the surgical instruments will be placed into the trochars.

Step 1: As the first step of the surgery, the surgeon will divide and staple the stomach using an endoscopic linear stapler into two pieces: a small upper section of the stomach (pouch) and a large bottom section. The pouch will be the size of a walnut.

Step 2: The second step is the bypass part. Your surgeon divides and connects a part of your small intestine to the pouch that has been made earlier. The food you consume will directly go into the small intestine right after it enters the stomach pouch.

The 3 types of gastric bypass

Various circumstances of personal health can give birth to the demand for different types of surgery. This includes gastric bypass.

There are 3 types of gastric bypass: mini gastric bypass, laparoscopic RouxenY gastric bypass, and open RouxenY gastric bypass. Let’s review what they are and see how they differ.

Mini gastric bypass surgery: The simplified version of the traditional gastric bypass. A long, vertical pouch is created for this procedure. It is performed on patients who have BMI between 30-40. It grants shorter hospital stays and faster recovery.

Laparoscopic RouxenY gastric bypass surgery: The traditional gastric bypass. A small pouch that’s the size of a walnut is created. It is for patients who have 40 and above BMI; and for patients who have 35-40 with an obesity-related medical condition.

Open RouxenY gastric bypass surgery: Instead of 3-4 incisions, 1 large incision (up to 10 inches) is made on the abdomen. It is performed on patients with super morbid obesity and super super-obesity (between 50 and >60 BMI). It carries more risks and requires a longer hospital stay.

Is gastric bypass permanent or reversible?

Some patients may ask “Is gastric bypass permanent?” and it is understandable for someone to ask this question as this is a life-altering procedure.

Gastric bypass is considered to be a permanent procedure. It is possible that it can be reversed because the stomach is not extracted from the body like it is in the gastric sleeve. However, it carries a great risk to do so because of its complexity. It carries the same complications as any bariatric surgery. Also, the functions of the stomach and the small intestine may never be the exact same again.

For these reasons, some surgeons may not be comfortable with performing a reversal surgery. If the surgeon of your choice is willing to perform the reversal surgery, make sure they have successfully done it before and are experienced in this field.

Who is qualified to perform a gastric bypass procedure?

Doctors who have done their general surgeon training are qualified to perform bariatric surgeries, including gastric bypass. Choosing your gastric bypass surgeon is one of the most crucial choices you are going to need to make. So it is more sensible to choose a bariatric surgeon, who specializes in bariatric procedures and who also has years of experience in bariatrics.

The benefits and drawbacks of gastric bypass surgery

Before going with a gastric bypass surgery plan, one needs to weigh all the benefits and drawbacks of it. Because it requires a lifestyle change due to being a life-changing procedure.

Let’s review the benefits of gastric bypass first:

  • Significant weight loss in 1-2 years with lasting outcomes
  • Can be performed minimally invasive
  • Can help manage or treat diseases related to obesity
  • Improves quality of life and confidence
  • Less calorie absorption out of foods

Now let’s talk drawbacks of gastric bypass:

  • Nutrient, mineral or vitamin deficiencies
  • Rare/low risk of complications
  • Temporary discomfort during recovery
  • Possibile weight regain if life adjustments are not made or kept
  • Side effects (dumping syndrome, hair loss, etc)

These drawbacks and possible complications may sound discouraging. But one should not have worries, for a specialized diet program is prepared for gastric bypass patients. For instance, for deficiencies and hair loss, you can ask your surgeon or your dietitian for appropriate optional supplements to manage and treat them. These precautions will also help decrease the risk of complications greatly.

From past to present: history of roux-en-y

The history of gastric bypass surgery can be considered to begin in 1954 by Kremen. He performed the first metabolic surgery: the jejunoileal bypass. This surgery was done via anastomosis (cross-connection) between the proximal jejunum (second/middle part of the small intestine) and distal ileum (third/final part of the small intestine). This procedure was devised to manage and/or treat dyslipidemia (imbalance of lipids). Unfortunately, as a result of this procedure, lowered lipid levels were observed in patients and they also suffered from severe diarrhea and dehydration. So, this procedure was not demanded by either the patient or the surgeon.

In 1966, Dr. Mason from the University of Iowa performed the firstbariatric surgery“: the open gastric bypass. This surgery involved cutting the stomach horizontally and creating a loop ileostomy. With this procedure, the third/final part of the small intestine is brought out of the skin creating a stoma; and a detachable pouching system is attached to it for draining the contents of the small intestine. Later on, it was changed to smaller pouches and stoma sizes. But this method caused severe bile reflux. So, a reconstruction was proposed: the “RouxenYloop where everything stays and happens inside the body. This, later on, became the standard for gastric bypass.

Comes 1994, the first laparoscopic gastric bypass was performed by Alan Wittgrove. With this method, bariatric and metabolic surgeries became popular swiftly. Some small alterations have been done concerning the surgery by numerous bariatric practitioners, and taken the form we use today.


(1) Seeras K, Philip K, Baldwin D, Prakash S. Laparoscopic Gastric Bypass. PubMed. Published 2022.

(2) Faria GR. A brief history of bariatric surgery. Porto Biomedical Journal. 2017;2(3):90-92. doi:

(3) Conner J, Nottingham JM. Biliopancreatic Diversion With Duodenal Switch. PubMed. Published 2022.

(4) Sudlow A, le Roux CW, Pournaras DJ. The metabolic benefits of different bariatric operations: what procedure to choose? Endocrine Connections. 2020;9(2):R28-R35. doi:

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