A Complete Guide to Bariatric Surgery


      Each type of bariatric surgery has pros and cons. 

Bariatric surgery, also known as weight loss surgery, refers to any surgical procedure for weight loss for people with obesity. 

All forms of bariatric surgery alter your digestive system, typically by modifying the stomach, to help you lose weight. This surgery can also provide other benefits, such as a reduced risk of diseases including type 2 diabetes and fatty liver disease.

While bariatric surgery is often an effective way to lose weight, it does come with risks. And it does require you to make permanent changes to your lifestyle to stay healthy and keep the weight off.

Here, discover what you need to know about bariatric surgery, as well as who might be a good candidate for these procedures.

Why Would You Need Bariatric Surgery?

People undergo bariatric surgery primarily to lose weight and improve obesity-related diseases if they have obesity. Doctors will consider bariatric surgery if other weight loss methods have not worked and the person’s overall health is at risk.

Among the selection criteria used to determine who is a candidate for bariatric surgery is body mass index (BMI), the calculation of a person's weight in kilograms divided by the square of their height in meters.

According to the American Society for Metabolic and Bariatric Surgery, doctors should consider bariatric surgery for:

  • People with a BMI of 35 or higher
  • Adults who have a BMI between 30 and 34.9 and a metabolic disease, such as diabetes
  • “Appropriately selected” children and adolescents

Doctors should also consider Asian people for bariatric surgery if their BMI is above 27.5.

When deciding whether or not someone should have bariatric surgery, doctors will also take into account various risk factors to ensure that it’s a safe option.

“We don’t want to do surgery if it’s not going to be safe for the patient,” says Ellen Morrow, MD, an assistant professor and surgeon at the University of Utah Health, who is certified in bariatric surgery.

These risk factors include smoking, substance use, and how well the patient is managing any mental health conditions they have.

Potential Benefits of Bariatric Surgery

If someone qualifies for the surgery, here are the potential benefits that may come with it.

Weight Loss

With bariatric surgery, weight loss is often dramatic. Around 90 percent of people lose half their excess body weight after bariatric surgery. If you have overweight or obesity, your excess body weight is the difference between your current body weight and ideal body weight.

While there is always a possibility of gaining back some weight, people who closely follow the special diet and other recommendations tend to have high rates of success keeping the weight off after surgery.

A 2021 study found that five years after bariatric surgery, there was “significant weight loss durability,” meaning that a significant amount of weight stayed off.

“So it is the most effective option if you’re looking at the weight loss outcomes,” says Morrow, “but there are definitely other benefits.”

Improvement to Obesity-Related Health Conditions

People with obesity have a heightened risk of serious diseases and conditions compared with people with a healthy weight. But if a person loses weight through bariatric surgery, many of these health problems can be improved.

“Even with a 10 percent body weight loss, we know that people will see a significant improvement in their health and weight-related medical problems,” says Morrow.

Those benefits can be even more dramatic with a higher amount of weight loss. “So especially with a 30 percent total body weight loss, you really can see remission of some weight-related medical problems, like diabetes, sleep apnea, high blood pressure, and high cholesterol,” says Morrow.

Here is a full list of diseases that may improve after bariatric surgery:

“I have worked with numerous patients with diabetes who have been able to discontinue their insulin or decrease their hypertensive medications,” says Kristen Smith, RD, a spokesperson for the Academy of Nutrition and Dietetics and a bariatric program manager at Piedmont Healthcare in Atlanta.

“It’s incredible to witness the improvement in lifestyle that many patients experience after bariatric surgery. Many patients are doing activities they haven’t been able to do for years, such as riding a roller coaster, flying on an airplane easier, or completing a 5K.”

Pain Reduction

If someone has obesity, chances are they may have pain in areas like their knees or hips. Obesity may damage the soft tissue of the joints, which can lead to osteoarthritis, a condition where joints become inflamed.

Bariatric surgery might help. In a 2022 study, researchers questioned almost 1,500 people (a majority of them women) about their pain before and after undergoing two common types of bariatric surgery.

The study followed up as long as seven years later and found that 41 to 64 percent of participants noted an improvement in their pain and physical function, as well as their ability to walk.

Longer Life

People with severe obesity who get bariatric surgery may be able to extend their lifespan, according to the NIH.

The American Society for Metabolic and Bariatric Surgery suggests that these procedures can reduce a patient’s risk of premature death by up to 50 percent.

One study from 2023 found that people who had bariatric surgery had 16 percent lower odds of all causes of death compared with the groups who did not receive the surgery.

Types of Bariatric Surgery and How Each Works

There are three main types of bariatric surgery that doctors currently perform. A fourth type — adjustable gastric band — is an older and more outdated procedure that has fallen out of favor due to the development of more effective techniques.

Each surgery has pros and cons. There are different average weight loss results and potential side effects or risks, says Morrow.

“In general, it seems like the risk of a procedure sort of parallels the benefits,” she adds. A sleeve gastrectomy, for example, may have a little bit less risk in some ways but results in a little bit less weight loss, while a duodenal switch has been shown to have potentially more long-term complications but also has the biggest weight loss results.

If you’re considering bariatric surgery, you’ll want to go over each with your doctor to determine which of these three types is the best option for you.

Sleeve Gastrectomy

This option is the most popular kind of bariatric surgery. “Sleeve gastrectomy is currently the most commonly performed procedure nationwide,” says Morrow.

The procedure involves removing 80 percent of the stomach. What remains is a stomach that’s about the size and shape of a banana.

In general, bariatric procedures work in one of two ways — or sometimes both, explains Morrow. “The first way is with restriction. All bariatric procedures have altered the stomach to try and make people have a smaller stomach and feel more full," says Morrow.

“A sleeve gastrectomy works purely through restriction, so we’re creating a smaller stomach by removing about two-thirds of the stomach, so conceptually it’s pretty simple.”

A sleeve gastrectomy is the simplest of the procedures and doesn’t require as much time on the operating table. “It takes approximately an hour to perform,” says Morrow.

Excess weight loss after sleeve gastrectomy can be anywhere between 30 and 80 percent.

Gastric Bypass

A Roux-en-Y gastric bypass is also known simply as a gastric bypass. "Roux-en-Y" is French for “in the form of a Y.” Like sleeve gastrectomy, this procedure is a common choice in the United States. 

“I personally and my colleagues here at the University of Utah perform Roux-en-Y gastric bypass the most, which is kind of considered the gold standard,” says Morrow.

In this procedure, the surgeon separates the stomach into a top and bottom section.

The top section — also called a pouch — is roughly the size of an egg and the bottom section no longer digests food. The surgeon then connects a part of the small intestine called the Roux limb to the new stomach pouch.

“The Roux-en-Y gastric bypass works through malabsorption, so for this procedure, there is some intestinal rearrangement as well to basically alter your body’s hormonal response to food, which is important,” says Morrow.

Malabsorption is where the body is unable to absorb nutrients from food properly. For a healthy person, malabsorption isn’t something that’s desirable, but in terms of bariatric surgery, it can be a benefit for weight loss, adds Morrow.

Limiting the digestion and absorption of nutrients reduces your calorie intake, allowing for weight loss. 

Because your body absorbs fewer vitamins and trace nutrients, it’s particularly important to follow the recommended diet after surgery to prevent unwanted side effects.

The surgery takes 90 minutes.

After this surgery, average weight loss is about 70 percent of excess body weight.

Duodenal Switch

Biliopancreatic diversion with duodenal switch is often referred to as simply a duodenal switch.

“A duodenal switch involves a bit more malabsorption [compared with the Roux-en-Y gastric bypass],” says Morrow.

The surgery has two key steps. The first is to perform a sleeve gastrectomy, so about 20 percent of the stomach remains.

The second step is to connect the end of the intestine to the duodenum, a tiny portion of the small intestine that connects to the stomach. This bypasses far more of the intestine than a gastric bypass. The result is that you’re unable to eat as much and or absorb as many nutrients.

This surgery can lead to more significant weight loss with patients losing around 80 percent of excess weight after this surgery, and it’s especially effective for patients with type 2 diabetes. But it comes with greater risks than other options, like malnutrition.

Duodenal switches also take around 90 minutes to 3 hours to perform, which is longer than other options.

While a specific diet is crucial for everyone who undergoes bariatric surgery, for people who have a duodenal switch, following eating guidelines closely is absolutely necessary.

“They have to be really careful about eating enough protein, or else they can become protein deficient, and drinking enough water, so they don’t get dehydrated, and they have to take vitamins every day, often more than once a day depending on which vitamin supplements they choose,” says Morrow.

How to Prepare for Bariatric Surgery

In the months leading up to bariatric surgery, your healthcare team will create a specific plan that will require making some lifestyle changes.

“I always tell patients, the more lifestyle changes you can make prior to surgery, the easier the transition after surgery will be,” says Smith. Here’s what a pre–bariatric surgery plan may look like.

1. Meet With Your Surgeon

Your surgeon will also likely meet with you to go over the procedure, review your medical history, and answer questions.

“In our program, the surgeons meet with the patients twice before surgery. That’s not true everywhere, but they should probably meet with their surgeon at least once,” says Morrow.

2. Get a Psychological Evaluation

Bariatric surgery calls for permanent dietary changes, making it a significant life change.

As a result, it’s important that a patient meet with a psychologist to make sure any conditions are treated or stabilized.

3. Meet Frequently With a Registered Dietitian-Nutritionist

A lot of education around how to eat after surgery needs to happen ahead of time. “It’s important for patients to learn about how they’re going to be able to eat with their new stomach, as well as what high-quality, nutritious foods we should all be focusing on,” says Morrow.

“There is a possibility for weight regain even after these procedures, so we want patients to understand that choosing high-quality food is going to be really important for them to maintain their weight loss in the long run,” she adds.

You’ll also likely discuss healthy eating strategies. “Patients are encouraged to practice mindful eating habits by listening to hunger cues, chewing their food adequately, and not eating in a distracting setting,” says Smith.

Many insurers will require a patient to undergo three to six months of medically supervised weight loss before bariatric surgery. “As a surgeon, the way I view it is that it’s our opportunity to provide education to the patient during that time period,” says Morrow.

4. Get Screened for Sleep Apnea

“We also like to screen all our patients for sleep apnea because it’s important that it gets treated before surgery if they do have it, since it’s pretty common among obese people,” says Morrow. 

One of the major risk factors for sleep apnea is obesity. Sleep apnea is a condition in which you stop breathing many times throughout the night. Breathing devices like continuous positive air pressure (CPAP) machines can help treat the condition.

5. Quit Smoking

If you smoke, you’ll need to quit well before bariatric surgery. “We would prefer that the patient has not been smoking within the past six months or a year, depending on which procedure they’re considering,” says Morrow.

Smoking is harmful for a number of reasons. “Smoking is going to increase the risk greatly of any major surgical procedure,” she explains. “It increases the risk for having [complications with] general anesthesia, it decreases your body’s ability to heal, and there are also some specific issues when it comes to bariatric surgery with regard to ulcer risk, particularly if someone is considering a gastric bypass.” 

A 2022 study also found that smoking increased the risk of postoperative wound complications.

What to Expect During Bariatric Surgery

On the day of surgery, patients can expect to receive general anesthesia. The surgery will take anywhere from an hour to a couple of hours, depending on the type of bariatric surgery the surgeon is performing. 

Most operations are laparoscopic procedures, which means the surgeon inserts a small instrument with a camera through a tiny cut in the abdomen. This technique can speed up recovery time compared with surgeries that require larger incisions.

Once the surgery is complete, you’ll wake in a recovery room. The staff will monitor you for complications, and you’ll likely need to stay a few nights in the hospital.

You may be walking the day of the surgery and sipping fluids while you’re still in the hospital.

 “All our patients are encouraged to get out of bed and walk within two hours of the surgery,” says Smith.

What Are the General Risks and Side Effects of Bariatric Surgery?

Risks and side effects can be minor or something you’ll need to see your doctor for. Here are some of the potential side effects and complications of bariatric surgery.

Side Effects

There are several mild side effects that can occur after bariatric surgery, while rarer side effects can have a bigger impact on a patient’s quality of life and health.

Potential side effects that can occur with bariatric surgery include:

Some people may need to have a second surgery or procedure.


While very uncommon, certain complications do come up after bariatric surgery.

“There are some significant complications that can happen that we worry about as surgeons, which are, fortunately, pretty rare,” says Morrow. “The rate of those more serious complications — blood clots and leaks — is around 1 percent.”

Signs of concern in a recovering patient include an abnormal heart rate, fever, and an unusual amount of pain, says Morrow.

Rare complications that can occur include:

  • Excessive bleeding
  • Infection
  • Problems relating to anesthesia
  • Blood clots
  • Leaks in your gut
  • Death

General Care After Bariatric Surgery

Receiving proper care after bariatric surgery is essential because of how it alters your gastrointestinal system. You’ll need to follow a special diet for life and be monitored by medical professionals each year.

Here is what care looks like after bariatric surgery.

Follow Specific Eating Guidelines

To prevent malnutrition or weight gain after bariatric surgery, you’ll need to follow a healthy way of eating and meet regularly with a registered dietitian.

“Hopefully patients meet with a dietitian regularly for at least the first year, and then we ask our patients to return annually after that,” says Morrow.

In the first month, the post-surgery diet requires a certain strategy. “I often refer to it as similar to feeding a baby,” says Smith. The diet progression starts with liquids, moves on to pureed food, and eventually reaches solid meals.

The diet may vary depending on the doctor or dietitian, says Morrow, but some of the main recommendations include:

  • Avoid soda.
  • Eat 60 to 100 grams of protein a day.
  • Drinking at least 64 ounces of water a day.
  • Eat frequent small meals.
  • Emphasize protein-rich foods.
  • Minimize refined carbohydrates.
  • Avoid food and drinks with refined sugars.

The healthfulness and quality of the foods you consume are also key. “Lean protein is definitely emphasized. Vegetables and dietary fiber should also be emphasized,” says Morrow.

In addition to helping you stick to a specific eating plan, a nutritionist may offer straightforward strategies for following the diet, such as meal planning.

Meet With Your Doctor

In addition to meeting with your dietitian regularly, you’ll meet with a medical or surgical provider regularly.

“I’m sure this varies based on where you have surgery, but in our program, we alternate between the surgeons and our physician assistants in terms of who is following up, because they are pretty frequent follow-up visits in the first year while patients are rapidly losing weight,” says Morrow.

After the first year, it typically becomes an annual visit, unless your doctor requests that you come more often.

Take Supplements

After bariatric surgery, you need to take supplements for life to prevent serious diseases that can come with vitamin and mineral deficiencies.

These supplements typically include:

Seek Mental Health Help if Needed

A lot of changes occur after bariatric surgery, and while scheduled appointments with a mental health professional are not part of the after care, they could be helpful for some.

Research suggests that it is common for people to use mental health services after bariatric surgery, with one study reporting that 1 in 6 people using a mental health service afterward.

So, be sure to raise any mental health concerns with your doctor if any come up.

The Takeaway

Bariatric surgery is an effective way to lose weight for people with obesity when other treatment options have not worked. Each type of weight loss surgery comes with potential benefits and risks and side effects, and requires a long-term commitment to making diet and other changes. “It’s imperative that patients understand the lifelong commitment to a healthier lifestyle,” Smith says. “Despite what the general public may believe, bariatric surgery is not the easy route for weight loss.”