A Complete Guide to Bariatric Surgery

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Each type of bariatric surgery has pros and cons.

With obesity rates continuing to climb in the United States, it may not come as a surprise that the number of bariatric surgeries is on the rise as well. While such surgeries are not a first-line treatment option, for many Americans with severe weight problems, they are an effective one, with studies showing that these procedures can reduce a patient’s risk of premature death by up to 50 percent, according to the American Society for Metabolic and Bariatric Surgery (ASMBS).

“Bariatric surgery is any surgical procedure that’s intended for weight loss,” says Ellen Morrow, MD, an associate professor and surgeon at the University of Utah Health, who is certified in bariatric surgery.

Bariatric surgery alters your digestive system, typically by modifying the stomach as well as sometimes the small intestines, to help a person lose weight, according to the Cleveland Clinic. This surgery can also provide other benefits, such as reducing the risk of diseases, including type 2 diabetes and fatty liver disease. “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.

While bariatric surgery is often an effective way to lose weight, it does come with risks, notes the Mayo Clinic, and requires a person to make permanent changes to their lifestyle to stay healthy and keep the weight off.

After surgery, though, there’s often a big change in a patient’s quality of life. “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,” says Smith.

Here, discover more of what you need to know about bariatric surgery, as well as who might be a good candidate for the procedure.

Common Questions & Answers

What are the four types of bariatric surgery?
Types of bariatric surgery include the sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion with duodenal switch. The adjustable gastric band is another type, but it has been performed less over the years.
What are the negatives about bariatric surgery?
Bariatric surgery may come with risks, including gastrointestinal issues (like vomiting and diarrhea), malnutrition, ulcers, hernias, and in very rare cases, issues like blood clots, infections, and leakage (which happens when the new connections haven’t fully healed).
What is the safest weight loss surgery?
Sleeve gastrectomy is a commonly performed bariatric surgery with the lowest risks. While a portion of the stomach is removed, the intestines aren’t impacted, which could reduce the risk of potential complications that can come along with malabsorption.
Who is eligible for bariatric surgery?
The National Institutes of Health criteria for bariatric surgery includes adults who have a body mass index (BMI) of 40 or more; adults who have a BMI of 35 or more as well as a serious health problem linked to obesity, like heart disease; and adults with a BMI of 30 or more with type 2 diabetes that is difficult to treat.
What is the life expectancy after bariatric surgery?
Research shows that bariatric surgery is associated with a longer life expectancy compared with nonsurgical treatments for obesity. One study found that the average life expectancy for people after bariatric surgery was years longer than for people in the control group.

Why Would You Need Bariatric Surgery?

People undergo bariatric surgery primarily to lose weight and improve obesity-related diseases. “Bariatric surgery does seem to be the most effective way to lose weight [for people with obesity], but it also involves some risk,” says Dr. Morrow. “It’s much lower risk than it used to be, and the safety is comparable to other abdominal surgeries that we frequently do, like gallbladder removal.” The risk of death from bariatric surgery is even considerably lower than, for example, hip replacement surgery, according to UCLA Health.

As for determining who is a candidate for bariatric surgery, the most widely used selection criteria was developed by the National Institutes of Health (NIH). It is largely based on 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 Centers for Disease Control and Prevention (CDC). Anyone who meets one of the following conditions qualifies, according to an NIH statement:

  • Adults who have a BMI over 40
  • Adults who have a BMI over 35 and also have significant weight-related medical problems
  • Adults who have a BMI of 30 or more and type 2 diabetes that is difficult to control even with medical treatments and lifestyle changes

“Some of the most common weight-related medical problems that qualify people are obstructive sleep apnea, sometimes reflux, high blood pressure, and heart problems,” says Morrow.

Medical professionals also must keep potential risks in mind when assessing who qualifies. “When it comes to reducing risk, we do have to think of patient factors that would affect that,” says Morrow. Smoking, for example, can be a risk factor for someone considering bariatric surgery. “We don’t want to do surgery if it’s not going to be safe for the patient,” Morrow says.

Mental health is also taken into consideration prior to surgery. “Substance use or mental health issues can be problematic,” says Morrow. “We certainly have a lot of patients who have had a mental health diagnosis or challenges, but we do want to make sure they’re getting support for that, and they’re well managed before they go through surgery.”

Potential Benefits of Bariatric Surgery

If someone qualifies for the surgery, here are the potential benefits of going through with it.

Bariatric Surgery Aids Weight Loss

With bariatric surgery, weight loss is often dramatic. According to the Cleveland Clinic, the average excess body weight loss 18 to 24 months after bariatric surgery is 50 percent (it also notes that some surgeries may help a patient lose more than others).

While there is always a possibility of gaining back some weight, post-op patients who closely follow the special diet and other recommendations tend to have high rates of success keeping the weight off. A study published in January 2021 in the International Journal of Surgery Open 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, but there are definitely other benefits,” says Morrow.

Bariatric Surgery Can Improve Health Conditions Related to Obesity

People who are classified as obese have a heightened risk of serious diseases and conditions (compared with people of a healthy weight), according to the CDC. 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 seen even more dramatically 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, according to the National Institute of Diabetes and Digestive and Kidney Diseases:

Bariatric Surgery Can Reduce Pain

If someone is obese, chances are they may have pain in areas like their knees or hips. Harvard Health Publishing notes that obesity may damage the soft tissue of the joints (potentially leading to osteoarthritis).

Bariatric surgery might help. A study published in September 2022 in JAMA Network Open questioned almost 1,500 people (a majority of them women) about their pain before and after undergoing two of the most 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.

Bariatric Surgery Can Potentially Lengthen Your Life

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

A study published in January 2023 in the journal Obesity 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

Three main types of bariatric surgery are currently performed. Although also still performed, 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, according to the ASMBS.

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.

Discover the low down on the three main surgeries. And note: If you’re considering bariatric surgery, you’ll want to go over each with your doctor to determine which 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, according to the ASMBS. 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.” The other way involves malabsorption (more on that later).

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. According to the Cleveland Clinic, excess weight loss after sleeve gastrectomy can be anywhere between 30 and 80 percent.

Roux-en-Y Gastric Bypass

Most people have heard the words “gastric bypass” but may not know its official name: Roux-en-Y gastric bypass (Roux-en-Y is French for “in the form of a Y,” according to the ASMBS).

Like sleeve gastrectomy, this procedure is performed frequently 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 stomach is separated into a top and bottom section (the top section — also called a pouch — is roughly the size of an egg), according to the ASMBS. The bottom section is no longer used to digest food (hence the word “bypass”), and a part of the small intestine (called the Roux limb) is connected right 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. 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.

One study explains that bariatric surgery that works through malabsorption limits the digestion and absorption of nutrients, which reduces a patient’s calorie intake, allowing for weight loss. Because vitamins and trace nutrients are also absorbed less, following the recommended diet after surgery is important to prevent unwanted side effects, the study notes.

Still, unlike in a duodenal switch (explained below), not as much of the intestinal area is impacted, which results in less malabsorption. “With Roux-en-Y gastric bypass, most of your intestinal area is still available for absorption, so we see fewer malabsorptive complications with that operation, although they can happen,” says Morrow.

After this surgery, according to the Cleveland Clinic, average weight loss is about 70 percent of excess body weight, and the surgery, according to UPMC, takes 90 minutes.

Biliopancreatic Diversion With Duodenal Switch

This surgery, often referred to as simply a duodenal switch, comes with the most potential weight loss, but it also has more potential risks. Per the Mayo Clinic, it's less common. “The duodenal switch is performed in some programs, and although we aren’t doing it at this time, I think it can be a good choice for some patients,” says Morrow. Per the Cleveland Clinic, it’s especially effective for patients with type 2 diabetes.

“A duodenal switch involves a bit more malabsorption [compared with the Roux-en-Y gastric bypass],” says Morrow. The surgery has two key steps, according to the Mayo Clinic. 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 — bypassing much of the intestine — to the duodenum (a tiny portion of the small intestine that connects to the stomach). This means the patient isn't able to eat as much and is limited in how many nutrients their body can absorb. While this can lead to more significant weight loss — according to the Cleveland Clinic, excess weight loss after this surgery is 80 percent — it can create more risks, like malnutrition, per the Mayo Clinic. It also takes longer to perform, around 90 minutes to 3 hours, according to UPMC.

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

A lot goes into the preoperative lead up to bariatric surgery, according to the ASMBS. A patient’s healthcare team will create a specific plan for them in the months and weeks before bariatric surgery, and it will require making lifestyle changes before the procedure. “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, discover what a pre-bariatric surgery plan may look like.

1. Meet With Your Surgeon

While you’ll have frequent meetings with a registered dietitian nutritionist, 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

This is another crucial pre-surgery meeting. Because the surgery calls for permanent dietary changes, it is a significant life change, and the ASMBS notes that 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

Many patients might assume that it’s crucial to meet with a registered dietitian nutritionist after their surgery, but it’s important to meet with your dietitian before surgery, too. “It's imperative that a patient work with a registered dietitian nutritionist prior to surgery to get counseling on how to make healthier lifestyle changes and to better understand the recommended dietary habits for after surgery,” says Smith.

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 are high-quality, nutritious foods that we should all be focusing on. 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,” says Morrow.

Healthy eating strategies will likely also be discussed. “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.

Morrow says that nutrition and medical teams like to make sure that there aren't any issues to address prior to surgery in terms of vitamin and mineral deficiencies.

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 patients during that time period,” says Morrow. In Morrow’s program, for example, there are five or more meetings with a dietitian prior to the surgery.

4. Get Screened for Sleep Apnea

One of the major contributors to the development of sleep apnea is obesity, according to a review. “We also like to screen all of 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. According to the National Heart, Lung, and Blood Institute, sleep apnea is when you stop breathing many times throughout the night; a breathing device like a continuous positive air pressure (CPAP) machine 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.

That’s because smoking is harmful for a number of reasons. “Smoking is going to increase the risk greatly of any major surgical procedure. It increases the risk for having 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 ulcer risk, particularly if someone is considering a gastric bypass,” says Morrow. A study published in February 2023 in the International Wound Journal found that smoking increased the risk of postoperative wound complications.

What Are the General Risks of Bariatric Surgery?

While bariatric surgery is an effective way to treat obesity, it comes with a set of risks, given that it is a major surgery. The following potential risks have been associated with bariatric surgery.

Excessive Bleeding

While it’s considered rare, gastrointestinal bleeding can occur after surgery. A review of research published in April 2022 in the journal Mini-Invasive Surgery notes that the rate of postoperative hemorrhage following bariatric surgery continues to decrease.

Infection

Infection in the incision site can happen after surgery, but according to Temple Health, this happens to less than 1.7 percent of people who have bariatric surgery. Other sources note that the rate of infection is as high as 5 percent.

Potential Problems Relating to Anesthesia

Even though anesthesia is generally pretty safe, according to the American Society of Anesthesiologists (ASA), there are still risks that something could go wrong. Certain conditions make anesthesia riskier, such as obesity, heart disease, and diabetes. Per the ASA, having obesity makes you more likely to have sleep apnea, which can also make anesthesia riskier (this is why sleep apnea should be treated before surgery).

Blood Clots

Blood clots are another rare risk. According to Columbia University Irving Medical Center, there’s a 1 percent risk of getting a clot in the legs after bariatric surgery, and the risk of the clot then breaking off and traveling to the heart or lungs is less than 1 percent.

Leaks in Your Gastrointestinal System

This is one of the most serious risks of gastric bypass surgery, but again, it’s incredibly rare. “It means that the new connections in the GI system don’t heal fully, and people can get sick from that,” says Morrow. According to Johns Hopkins Medicine, these leaks can happen in 1.5 to 6 percent of bypass procedures and mostly happen within three days of the surgery.

Extremely Rarely, Death

Bariatric surgery has been found to lower a patient’s odds of premature death, according to research published in February 2023 in the journal Obesity. Still, the procedure itself carries an incredibly slight risk of death. According to a study published in November 2021 in the journal Obesity Surgery, the average 30-day mortality risk after surgery was 0.19 percent (with the risk of death higher for men than for women).

What to Expect During Bariatric Surgery

On the day of surgery, patients can expect to receive general anesthesia (Penn Medicine notes that patients are asleep for the whole surgery). The surgery will take anywhere from an hour (possibly less) to a couple of hours, depending on the type of bariatric surgery the surgeon is performing. A sleeve gastrectomy, for example, will be a shorter procedure than, say, a duodenal switch.

According to the Mayo Clinic, most surgeries are performed laparoscopically, which means a small instrument with a camera is inserted through a tiny incision in the abdomen. This technique can help speed up recovery time compared with surgeries that require larger incisions.

Once the surgery is complete, you’ll wake in a recovery room, the Mayo Clinic notes, where you’ll be monitored for complications, and you’ll likely need to stay a few nights in the hospital. According to Penn Medicine, you may be walking the day of the surgery and sipping fluids while you’re still in the hospital. “All of our patients are encouraged to get out of bed and walk within two hours of the surgery,” says Smith.

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

Side effects can be minor or something you’ll need to see your doctor for ASAP. “The most common are probably gastrointestinal side effects, which makes sense because that’s the system we’re operating on,” says Morrow. Here, discover some of the common — as well as extremely rare — side effects and complications of bariatric surgery.

Complications

While very uncommon, certain complications 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.”

So what are some signs of these more serious yet rare complications? Signs of concern in a recovering patient include whether their heart rate is normal, whether there is any fever, and whether they are having a normal amount of postoperative pain, says Morrow. The rare complications that can occur (but, again, are extremely uncommon) include:

  • Blood clots
  • Leaks in the gastrointestinal system
  • Infection
  • Excessive bleeding
  • Problems relating to anesthesia
  • Extremely rarely, death

Side Effects

Certain side effects after bariatric surgery are considered minor, while other, more rare side effects can have a bigger impact on a patient’s quality of life and health. These are the potential side effects that can come along with bariatric surgery, according to the Mayo Clinic:

  • Bowel obstruction
  • Dumping syndrome (according to the Cleveland Clinic, when a person’s stomach empties what’s inside too quickly into the small intestine, which can cause nausea, vomiting, diarrhea, and abdominal pain)
  • Gallstones
  • Hernia
  • Low blood sugar, called hypoglycemia
  • Malnutrition
  • Ulcers
  • Vomiting
  • Acid reflux
  • The need for a second, or revision, surgery or procedure
  • Rarely, death

General Care After Bariatric Surgery

Receiving proper care after bariatric surgery is essential because bariatric surgery alters your gastrointestinal system. You’ll need to follow a special diet for life and be monitored by medical professionals annually (more frequently in the first year). Here is what care will look like after surgery.

Follow Specific Eating Guidelines

To prevent malnutrition or weight gain after bariatric surgery, patients 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, advances to pureed food, and eventually reaches solid textures, Smith adds (and the Mayo Clinic concurs).

The diet may vary depending on the doctor or dietitian, says Morrow, but some of the main recommendations are no soda, at least 60 grams of protein a day, and 64 ounces of water a day.

In general, Smith describes the post-surgery dietary guidelines as frequently eating small meals, emphasizing protein-rich foods, and minimizing refined carbohydrates, as well as avoiding food and drinks with refined sugars.

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

Smith usually avoids the word “diet” when referring to the plan. “I try to refer to the eating pattern after bariatric surgery as a new, healthier lifestyle,” she says.

In addition to helping patients stick to the specific eating plan, a nutritionist may offer straightforward strategies for following the diet. “A really important factor is learning how to shop and meal plan, because a lot of us make fewer healthy choices when we don’t have a plan and aren’t prepared — convenience choices,” says Morrow.

Smith encourages patients to stick with the follow-up care. “I’ve seen many patients afraid or embarrassed to have follow-up visits because they are struggling to maintain a healthier lifestyle, but I try to remind patients that the whole bariatric team, including the registered dietitian nutritionist, is there to help,” says Smith.

Meet With Your Doctor

In addition to meeting with your dietitian regularly, you’ll meet with a medical or surgical provider regularly, says Morrow. “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’re 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. “We ask our patients to return annually after that first year. Not everyone is always able to do that if they move or change insurance, but we’d like to have long-term follow-up with our patients,” says Morrow.

Take Supplements

After bariatric surgery, you need to take supplements for life, according to the ASMBS, to prevent serious diseases that can come along with vitamin and mineral deficiencies. These supplements typically include a multivitamin, vitamin B12, calcium, vitamin D, and iron.

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. The ASMBS notes that relationships, for example, can be impacted due to more stress and potential shifts in body image. Still, just know that you’ll have to be your own advocate and raise any mental health concerns with your doctor.

Summary

Bariatric surgery is the most effective way to lose weight. Still, each type of weight loss surgery comes with potential risks and side effects, and requires a lifelong commitment to making diet and lifestyle 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.” While it may be a good fit for some, it might not be right for everyone. Discuss with your doctor whether the surgery could be a good choice for you.

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