Weight loss surgery

Photo of an overweight patient having his blood pressure measured

Weight loss surgery can help obese people lose a lot of weight and improve their health. But there’s a risk of complications, some of which can be serious. You also have to make a lot of changes after the surgery, in order to prevent digestive problems and malnutrition. So it's important to have good after-surgery care too.

Surgery (such as gastric sleeve surgery) may be an option for people who are very obese or have accompanying conditions like diabetes. The goal of surgery may be to lose a lot of weight quickly or to treat metabolic disorders like diabetes. Weight loss surgery is also called bariatric surgery (from the Greek word “baros,” which means weight). If the aim of the surgery is to treat a metabolic disorder, it is called metabolic surgery.

Removing body fat (liposuction) isn't a treatment option for obesity because it hardly affects the intake and burning of calories, and it's associated with risks. It also doesn't have any proven health benefits.

When is weight loss surgery considered?

German medical societies currently recommend only considering surgery for people with

  • a BMI of 40 or more (class 3 obesity) or
  • a between 35 and 40 (class 2 obesity) in people with additional conditions like diabetes, heart disease, or sleep apnea.

But surgery is usually only considered when other weight loss attempts are unsuccessful – for example, when a supervised weight loss program with dietary advice and exercise has not led to enough weight loss. Sometimes surgery is an option for people who have never tried to lose weight before. For instance, people who have a over 50 or a severe accompanying illness.

What should you know before deciding?

When deciding whether to have surgery, it’s important to carefully consider the pros and cons. Weight loss surgery can help you lose a lot of weight, and that can improve your health and quality of life. It also has a positive effect on related medical conditions, especially diabetes, sleep and high blood pressure. But it can lead to various complications and have life-long effects. Losing weight very rapidly may also cause gallstones to develop.

After the surgery, you have to make long-term lifestyle changes (for example, to your diet) and have regular check-up appointments. Many people gain a little weight again several years after weight loss surgery.

How can surgery help in the treatment of obesity?

Various kinds of gastric (stomach) surgery can be used to treat obesity. The most common ones are

  • Gastric banding: An elastic band is placed around the stomach so that less food fits into it and you feel full faster. The band can be removed again. It is only recommended in certain situations.
  • Gastric sleeve surgery (sleeve gastrectomy): The size of the stomach is surgically reduced so it can hold less food.
  • Gastric : This procedure involves reducing the size of the stomach and also shortening the digestive tract so that fewer nutrients and calories are absorbed from the food. There are various kinds of gastric surgery: The standard one is called a Roux-en-Y . There is also a special kind of known as a "mini" or "omega loop" gastric .

Gastric surgery and gastric sleeve surgery lead to hormonal changes that reduce your appetite and affect your metabolism. That can have a positive influence on the treatment of metabolic disorders like diabetes. But it's not clear whether that can prevent the development of health problems caused by the metabolic disorder.

Many people feel more physically fit after surgery due to the weight loss. It is easier to do exercise and sports, and more enjoyable too. Many people get positive feedback and compliments from friends and family after the surgery. Some also say the surgery helped them to perform better at work and have a more satisfying sex life.

What are the pros and cons of gastric banding?

Gastric bands artificially reduce the size of the stomach by squeezing it. They consist of a ring-shaped silicone band that is placed around the upper part of the stomach. This creates a small pouch that can’t hold as much food as the stomach could before, so you feel full faster.

Illustration: Gastric band

The gastric band is filled with salt water, which makes it possible to tighten or loosen it after surgery: With the help of a syringe, liquid can be drained or added through a tube. The access to it (port) is placed under the skin and is about the size of a coin. If, for example, the gastric band is too tight and causes vomiting, it can be loosened.

Gastric bands do not influence how well nutrients are absorbed. They can be removed again, so the procedure is reversible. Because of this, it is particularly suitable for young women who want to have children in the future. But sometimes it's difficult to remove the gastric band due to adhesions (when different pieces of tissue become stuck together).

Usually, your body weight drops by about 10 to 25% in the first year after gastric band surgery. This means that someone who weighs 130 kilos can lose 10 to 30 kilos. Your weight may continue to drop a bit in the second and third year after surgery, too.

In studies comparing the different types of surgery, gastric banding was less effective than gastric sleeve surgery and surgery. Sometimes gastric bands don't lead to enough weight loss. Then the band can be taken off again, and doctors might consider surgery to remove some of the stomach instead.

The possible side effects of a gastric band include heartburn and vomiting, for example if the band is too tight. Gastric bands may also move, grow into or through the stomach wall, or tear. Sometimes, they then have to be replaced or removed. In studies, about 8 out of 100 people who had gastric banding had complications. Up to 45 out of 100 people have follow-up surgery at some point – for example, because they haven't lost enough weight or there’s a problem with the gastric band.

What are the pros and cons of gastric sleeve surgery?

In gastric sleeve surgery (sleeve gastrectomy), about three-quarters of the stomach are surgically removed. The stomach looks a bit like a sleeve after the operation. That's where it gets its name from.

Illustration: Gastric sleeve surgery (sleeve gastrectomy)

After gastric sleeve surgery, people who are obese usually lose about 15 to 25% of their body weight in the first year. So someone who weighs 130 kilos could expect to lose about 20 to 30 kilos after this operation.

Gastric sleeve surgery can have various side effects: Eating too much can cause heartburn and vomiting. Complications may occur during or after surgery. For example, the stomach might start leaking along the edge that was cut, and then further surgery is needed. In studies, about 9 out of 100 people had a complication during or after this surgery, and 3 out of 100 needed further surgery. Less than 1 out of 100 people died during surgery or due to complications.

Gastric sleeve surgery can’t be reversed. If an obese person doesn’t lose enough weight after gastric sleeve surgery, they could have another procedure (like gastric surgery) later.

What are the pros and cons of gastric bypass surgery?

Gastric surgery is more complex than gastric banding or gastric sleeve surgery. The name "" comes from the fact that the food no longer passes through the entire stomach and small intestine, but instead bypasses much of it.

During Roux-en-Y surgery, a small part of the stomach (that can hold about 20 milliliters) is separated from the rest of the stomach. It forms a pouch that is then connected to the small intestine. The rest of the stomach is closed off with stitches or staples, and is no longer connected to the food pipe. The food then goes directly from the newly formed pouch into the small intestine.

To make sure that digestive juices from the gallbladder, , and bypassed stomach still reach the intestine, the upper part of the small intestine (leading from the bypassed stomach) is connected to the rest of the small intestine in a different place.

Illustration: Roux-en-Y gastric bypass

Studies have shown that gastric surgery (like gastric sleeve surgery) usually helps obese people to lose 15-25% of their body weight in the first year after the operation. The weight comes off quite quickly, and typically stabilizes within one to two years.

Based on what doctors now know, gastric surgery leads to greater long-term weight loss than other procedures do. Gastric surgery can have positive effects on related medical conditions like diabetes, too.

Sometimes gastric surgery is more suitable than gastric sleeve surgery – for example, in people who have reflux problems. In other words, if their stomach juices flow up into their food pipe.

There is also another kind of gastric surgery, known as a mini . Unlike in a Roux-en-Y , only one new connection is made here (not two): The stomach pouch and small intestine are joined together. Here, too, the remaining part of the stomach is no longer used.

Side effects and surgical risks

There are two common long-term effects of gastric surgery, known as early dumping syndrome and late dumping syndrome. In early dumping syndrome, a lot of undigested food passes into the small intestine too quickly. The body tries to “dilute” the unusual amount of nutrients, and a lot of water suddenly passes from the blood vessels into the small intestine. You then have less liquid in your bloodstream as a result, and your blood pressure drops. This can cause drowsiness, nausea, stomach ache, and sweating. Early dumping syndrome is especially common after eating very sugary foods. It usually happens within 30 minutes of eating.

Late dumping syndrome is less common. Here the body releases too much insulin, which leads to low blood sugar levels with typical symptoms like dizziness, feeling weak, and sweating. It can occur one to three hours after eating, especially after eating carbohydrate-rich foods.

The risks of surgery include scarring in the small intestine, internal hernias, and leaking at the new connection between the stomach and intestine if it doesn't seal properly. All of these complications might have to be treated with more surgery. In studies, 12 out of 100 people had complications; 5 out of 100 people needed to have more surgery.

In rare cases, life-threatening complications may occur during surgery or in the first few weeks after surgery. For example, blood poisoning can develop if one of the new connections starts to leak and stomach contents get into the abdominal cavity. In studies, fewer than 1 out of 100 people who had gastric surgery died during the surgery or as a result of complications.

Preparing for surgery

In the weeks leading up to weight loss surgery, doctors often recommend that you go on a diet or take medication to lose some weight. The idea is to make the surgery itself easier. One reason is because losing weight causes the liver to shrink a little and makes it easier to perform surgery where the food pipe joins the stomach.

Before surgery, various examinations are done to check for any medical reasons not to have the operation. This includes laboratory tests, a gastroscopy using a flexible tube to see the inside of the stomach, and an ultrasound scan of the abdomen (belly). A psychological examination can be helpful too – for example, to see if you have an eating disorder that is caused by psychological issues. Then psychological treatment may be more suitable.

Which surgery is suitable for you and what does it involve?

Your surgery options will depend on your expectations and how you feel about the pros and cons of the different approaches. Other things that play a role include your overall health, weight, and any other medical problems you have. The type of work you do might influence the decision too. It is advisable to have the surgery carried out by a surgeon who is experienced in performing that kind of operation. There are treatment centers in Germany that are certified (by the German Society for General and Visceral Surgery, DGAV) to perform weight loss surgery. These centers meet special requirements regarding the equipment used and the doctors' experience with this surgery.

Weight loss surgery is usually minimally invasive (keyhole surgery). In an approach known as laparoscopy, special endoscopes are inserted into your abdominal cavity (belly) through several small cuts. Endoscopes are flexible tubes with a light, camera and sometimes instruments at the end of them.

You usually have to stay in the hospital for a few days after having minimally invasive surgery.

Lifestyle changes after surgery

After the surgery, you might not be able to eat any solid foods for several weeks. Depending on the type of surgery, you may eat only liquid foods (like water and broth) at first, and then start eating soft foods (like yogurt, pureed foods, mashed potatoes). After a few weeks, solid foods are introduced gradually so the stomach and bowel can slowly get used to them again.

It is important to get professional dietary advice after weight loss surgery, in order to prevent digestive problems like heartburn, stomach ache, nausea, and vomiting. Depending on the type of surgery, you may have to

  • eat small servings.
  • eat slowly and chew well.
  • not eat and drink at the same time because the stomach isn't big enough to hold both. It is important not to drink anything for 30 minutes before and after eating.
  • avoid fatty and sugary foods and drinks because they can cause digestive problems. Especially after gastric surgery, very sugary foods and drinks can cause serious side effects due to dumping syndrome. Examples include things like candy, fruit juices, soft drinks and ice cream.
  • drink alcohol in moderation because the body may absorb it much faster. This is particularly true after gastric surgery.

Diet changes after the surgery

After weight loss surgery, especially gastric surgery, the digestive tract can’t absorb vitamins and nutrients as well as it used to. You will have to take dietary supplements for the rest of your life in order to prevent malnutrition. That includes and vitamin D supplements, for example, to keep your bones strong and prevent osteoporosis – and vitamin B12, , iron, and zinc, to keep your blood and healthy.

Regular blood tests are also recommended in order to look out for signs of malnutrition – first after six months and then once a year after that. Fewer dietary supplements are needed after gastric banding than after gastric sleeve or gastric surgery.

There is also a risk that the body will break down muscle tissue as well as fat after the surgery. To prevent that from happening, doctors recommend eating a high-protein diet and getting enough physical exercise or doing sports regularly. That can help you lose weight, too.

Cosmetic consequences

Major weight loss often leads to excess, loose skin that hangs from the body. Many people find their skin folds and loose skin unattractive and feel unhappy about it. Some would like to have their skin removed or tightened, but statutory health insurers will only pay for this procedure if the loose skin causes medical problems or severe psychological distress. Large skin folds can cause infections or rashes, for example. So it's important to have a good skin care routine. If you would like to have plastic surgery after losing weight, you should get in touch with your health insurer and find out if they will cover the costs of the treatment.

Who can you talk to before you decide?

Weight loss surgery is a major procedure, and you have to make long-term changes to your lifestyle and daily routine afterwards. So it’s important to find out about the consequences of the surgery before you decide to have it. A list of questions can help you prepare for your doctor's appointment.

When considering the pros and cons of the different types of surgery and the changes you have to make after surgery, it is best to talk with experts who know the treatment well. These include doctors in specialized doctor's offices and hospitals, as well as psychologists, dietitians and nutritional therapists who know all about how the surgery can affect your life. Support groups can help you to file applications with your health insurance, for example.

Possible questions include:

  • Is surgery an option for me and, if so, which kind of surgery?
  • What are the possible risks and side effects, and how common are they?
  • What are the chances of success? What are the chances of needing more surgery after?
  • How much weight loss can I expect after surgery?
  • What health benefits can I expect?
  • How will I have to change my diet after surgery?
  • Which foods might I not tolerate as well after the operation?
  • Which dietary supplements will I need after surgery to get enough nutrients?
  • How many check-up appointments will I need?
  • Who will provide my after-surgery care?

People don’t always get the help and advice they need before and after surgery. This can lead to false expectations and cause problems in everyday life. Support groups can help you find the support you need.

What if you want to have children?

Women can generally get pregnant and have healthy babies after weight loss surgery. But if you want to have children, it’s important to talk with your doctor about possible risks – for example, whether you would need additional tests or dietary supplements to make sure you get enough nutrients. Doctors generally advise women not to get pregnant in the first twelve months after weight loss surgery. This is because your body loses a lot of weight and the baby wouldn't get enough nutrients during that time.

Will your health insurance cover the costs of weight loss surgery?

In general, statutory health insurers in Germany can cover the costs of weight loss surgery. First, you have to file an application together with your doctor and include a note from the doctor. The surgery is only approved if certain requirements are met.

  • The operation needs to be medically necessary, and you must have tried other treatment options that ended up not helping enough.
  • Your doctors need to have ruled out any treatable medical conditions that can lead to obesity. These include an underactive thyroid gland (hypothyroidism) or an overactive adrenal cortex.
  • There should be no important medical reasons not to have the surgery. Examples of such reasons include health problems that make surgery too risky, pregnancy, a drug or alcohol dependence, and serious mental disorders that make it harder for you to make the necessary lifestyle changes after surgery.

You also have to show that you are willing to get enough exercise after surgery and eat a healthy diet. To do this, you will typically have to add a "letter of motivation" and other documents to the application. These may include a food diary, certificates to prove that you have participated in weight loss programs or had professional dietary advice, and certificates to show that you have participated in exercise classes.

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Created on November 22, 2022

Next planned update: 2025


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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