Frequently Asked Questions About Weight Loss Surgery

Medically Reviewed by Arefa Cassoobhoy, MD, MPH on March 23, 2023
8 min read

How does weight loss surgery work, and could it help you? Get answers here to frequently asked questions about weight loss surgery.

Weight loss surgery is not for everyone. Doctors generally recommend it only for people who:

  • Have a body mass index (BMI) of 40 or more -- about 100 pounds overweight for men and 80 for women
  • Have a lower BMI (35 to 40), but also have serious health problems related to obesity such as heart disease, type 2 diabetes, high cholesterol, or severe sleep apnea
  • Have tried and failed to lose weight by nonsurgical means such as diet and exercise
  • Fully understand the risks associated with weight loss surgery and are motivated


There are two basic types of weight loss surgery -- restrictive surgeries and malabsorptive surgeries (and also surgeries that are a combination of both procedures). Each helps with weight loss in different ways.

  • Restrictive surgeries (like adjustable gastric banding) work by physically restricting the stomach's size, limiting the amount of solid food you can eat. A normal stomach can hold about three pints of food. After weight loss surgery, a stomach may only hold one ounce of food, although over time it may be able to hold two or three ounces of food.
  • Malabsorptive surgeries (like gastric bypass) work by changing the way your digestive system absorbs food. This type of weight loss surgery is more complicated. The surgeon removes parts of your intestine, creating a shortcut for the food to be digested. This means that fewer calories get absorbed into the body. The combined malabsorptive/restrictive surgery also creates a smaller stomach pouch, which restricts the amount of food you can eat.

Gastric Banding Surgery

The Pros:

  • Gastric banding is often a minimally invasive surgery performed with small incisions, a laparoscope (a tiny camera), and special instruments.
  • There is no need to cut into the stomach or intestine, and recovery is usually faster than with gastric bypass surgery.
  • The surgery can be reversed by surgically removing the band.
  • The band can be tightened or loosened in the doctor's office to control weight loss and nutritional needs. To tighten the band, saline solution is injected into the band. To loosen it, the liquid is removed with a needle.
  • Serious complications are uncommon. But gastric bands can slip out of place, become too loose, or leak. Should this occur, additional surgery may be necessary.

The Cons:

  • Your weight loss may be less dramatic than with gastric bypass. The average loss is 40% to 50% of your excess weight -- although not in everybody.
  • You may regain some of the weight over the years. 
  • This type of surgery has a higher rate of re-operation.

Gastric Bypass Surgery

The Pros:

  • Weight loss is quick and dramatic. People lose an average of 60% to 80% of their excess body weight.
  • Because weight loss is quick, weight-related health problems such as diabetes, high blood pressure, high cholesterol, arthritis, sleep apnea, and heartburn improve quickly.
  • Most people are able to keep at least 50% of the excess weight off long term.
  • Loss of stomach tissue results in a drop in the so-called "hunger hormone" (ghrelin), which helps control appetite.

The Cons:

  • Gastric bypass surgery is riskier and is associated with more complications.
  • The surgery may result in vitamin and mineral deficiencies.
  • The surgery may result in dumping syndrome, which occurs when food moves too quickly through the stomach and intestines. Dumping syndrome can cause shaking, sweating, dizziness, nausea, and severe diarrhea.
  • Gastric bypass is generally considered irreversible. The surgery permanently changes how your body digests food.


Typical risks associated with weight loss surgery include:

  • Vomiting from eating too much too quickly and not chewing well
  • Constipation
  • Nutritional deficiencies such as anemia and osteoporosis.

As with any surgery, wound infections can occur up to three weeks after surgery. These can be treated with antibiotics, and sometimes require further surgery.

Complications that may develop following weight loss surgery include:

Rare but serious complications include:

  • Bleeding in the stool, or black stools
  • Leaks in new connections made by weight loss surgery; these usually occur within five days of surgery.
  • Blood clots in the lungs, called pulmonary emboli, rarely occur, but if they do, they are the most common cause of death after weight loss surgery. Blood clots can be usually prevented with blood thinning medicines and frequent activity.
  • Blood clots in the legs, called deep vein thrombosis, or DVT
  • Pneumonia


After gastric bypass surgery, most people can expect to lose between 66% and 80% of their extra body weight.  Most of this is lost within the first two years.

After gastric banding, people lose 40% to 50% of their extra weight, typically within the first two years after the surgery. 


Obesity-related medical problems will generally improve after weight loss surgery. These include:

  • Obstructive sleep apnea
  • Type 2 diabetes
  • Gastroesophageal reflux disease (GERD)
  • High cholesterol
  • Degenerative joint disease or orthopedic problems
  • High blood pressure
  • Asthma
  • Urinary incontinence


After weight loss surgery, the body has difficulty absorbing certain important nutrients, including:

  • Iron
  • Vitamin B-12
  • Folate
  • Calcium
  • Vitamin D

However, taking a daily multivitamin, plus other supplements, can prevent or reduce these deficiencies.

Over time, some people regain weight despite bariatric surgery. Some eat high-calorie or high-fat foods instead of healthy foods -- and eat them too often. Some people rely on "soft meals" such as ice cream and milk shakes.

The body itself may change over time, too, leading to weight gain. The digestive tract might begin absorbing more calories. Even the size of your surgical stomach can expand gradually over time.

To keep the weight off, you need to work at it. Here are some tips:

  • Eat very small meals. Adapting to small meals is challenging but necessary. Eat small amounts of food slowly, chew well, and eat lots of protein.
  • Make nutrition a priority. You must make the foods you eat count. Good nutrition is critically important. You must also take the right supplements, as recommended by your health care provider, because serious malnutrition occurs easily following weight loss surgery. A dietitian can create a diet and nutrition plan designed to meet your needs.
  • Exercise regularly. Many obese people aren't used to exercise, but it's very important to prevent weight regain. The good news: Once you start losing weight, exercise will get easier.

As you start losing weight, you will likely be thrilled with your new appearance. However, many people who lose a lot of weight often find their skin looks loose and baggy. You may want plastic surgery to remove this excess skin.

Your relationships with friends and family may indeed change after weight loss surgery. For many people, food and drink are the basis for socializing. After weight loss surgery, you must find other ways to socialize -- ways that aren't focused on food.

Also, as you lose weight, the results will be obvious. People will notice, and ask you about your appearance. Prepare for these questions ahead of time -- and consider how you want to answer them.

Losing a significant amount of weight is no small matter. In fact, the effects are profound and far-reaching. Life may seem disconcerting at times. You may feel odd, not quite like yourself. You may feel overwhelmed by the lifestyle changes you must make for the rest of your life. You may have reached for food as comfort -- and have difficulty giving it up.

A therapist can help you get through this complicated period. A support group can also help. Ask your doctor about support groups for people who have had weight loss surgery. It helps to meet people who are making the same adjustments you're making -- and can help keep you on track with your weight loss program.

A typical weight loss surgery can run from $15,000 to $25,000 -- so insurance coverage is critical for most people. Every insurance company is different, but before agreeing to cover the surgery, most insurance companies want documentation of the patient's struggle with obesity. They want a primary care doctor's records indicating that the patient has tried to lose weight through diet, exercise, and psychological counseling. Also, medical causes of obesity must be ruled out. It pays to ensure that your doctor documents your efforts early on, so surgery is an option later.

Clearly, you want a bariatric surgeon who is very experienced in this specialty area. Research shows that the more experienced the surgeon, the lower the risk of death or complications during or after the surgery.

To identify an excellent surgeon, collect a list of names. Ask friends and family members. Ask coworkers. You might be surprised -- lots of people often know others who have had weight loss surgery and want to share their doctor's name.

Check into centers and hospitals offering educational seminars for people considering weight loss surgery. You can learn more about the actual procedure, the benefits and the risks. You may also get names of specialists who perform these surgeries. Go to these seminars and ask questions.

Here are some questions to consider when choosing a bariatric surgeon:

  • Is the specialist board certified by the American Board of Surgery?
  • Is the specialist a member of the American Society of Bariatric Surgeons?
  • How many weight loss surgeries has the surgeon performed? (100 or more is ideal.)
  • How many of the surgeon’s patients have died from weight loss surgery? (Less than 1% is the average.)
  • How often do patients have complications? What side effects are most common?
  • What is the surgeon's success rate?

Don't rush into weight loss surgery. Talk to family and friends. Talk to surgeons and to people at the hospital centers. Prepare yourself mentally and physically. Make sure you are committed to changing your lifestyle and to keeping the weight off forever.

Show Sources

News release, Allergan.
Sjöström, L. New England Journal of Medicine, December 2004.
WebMD Medical Reference: "What to Expect After Weight Loss Surgery;" "Your Options in Weight Loss Surgery: Making the Choice;" "Preparing for Weight Loss Surgery;" "Life After Weight Loss Surgery;" and "Is Weight Loss Surgery for You?"

American Society for Metabolic and Bariatric Surgery: "Bariatric Surgery Procedures."

Cleveland Clinic. 

National Institute of Diabetes and Digestive and Kidney Diseases.

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