Weight loss surgery

Weight-loss surgery can help people with severe obesity lose a lot of weight. Here is how it works, who it is for, and the trade-offs.

For most people, eating differently and being more active are the foundation of weight loss. But obesity is a chronic disease, and for some people with severe obesity, diet and exercise alone don't bring enough lasting weight loss to protect their health. Weight-loss surgery, also called bariatric or metabolic and bariatric surgery, is one of the most effective treatments available for them. It is major surgery, though, and it comes with lifelong changes.

How it works

Bariatric surgery makes the stomach smaller, and some procedures also reroute part of the small intestine. People feel full sooner and eat less, and the operations change gut hormones that affect hunger, fullness and blood sugar. Most procedures today are done laparoscopically, through several small incisions, which shortens recovery compared with open surgery.

The main procedures

  • Sleeve gastrectomy. The surgeon removes most of the stomach, leaving a narrow tube or "sleeve." It is the most common procedure in the United States.
  • Roux-en-Y gastric bypass. The surgeon creates a small stomach pouch and connects it directly to the middle part of the small intestine, so food bypasses most of the stomach and the first part of the intestine.
  • Duodenal switch (biliopancreatic diversion with duodenal switch). A sleeve gastrectomy combined with a larger intestinal bypass. It tends to produce the most weight loss but carries a higher risk of nutritional deficiencies.
  • Adjustable gastric band. An inflatable band placed around the top of the stomach. It was popular in the 2000s, but it is now rarely used, because weight loss tends to be smaller and many bands later need to be removed.

Who may qualify

Guidance from the US National Institute of Diabetes and Digestive and Kidney Diseases says surgery may be an option for adults with a body mass index (BMI) of 40 or more, or 35 or more with a serious obesity-related health problem such as type 2 diabetes or sleep apnea. Updated guidelines published in 2022 by the American Society for Metabolic and Bariatric Surgery and the International Federation for the Surgery of Obesity and Metabolic Disorders go further: they recommend surgery for adults with a BMI of 35 or more, and say it should be considered from a BMI of 30 for people with metabolic disease. Insurance rules vary. You can check your BMI with our BMI calculator.

Candidates usually go through medical, nutritional and psychological assessments first, to make sure surgery is safe for them and that they are ready for the changes it requires.

Benefits

Many people lose a substantial amount of weight, typically much more than with diet and exercise alone, and keep much of it off for years. Weight-related conditions often improve or go into remission, especially type 2 diabetes, high blood pressure and sleep apnea.

Risks and lifelong changes

Like any major surgery, bariatric surgery carries risks, including bleeding, infection, leaks from the staple lines and blood clots. Later problems can include gallstones, ulcers, narrowing where the stomach or intestine was joined, and "dumping syndrome" after sugary foods, which causes nausea, cramps and diarrhea. Some people need another operation.

Because people eat much less, and some procedures reduce absorption, vitamin and mineral supplements are needed for life, along with regular blood tests. Patients must learn to eat small portions slowly, prioritize protein and avoid drinking with meals. Some people regain weight over the years, which is why ongoing follow-up with the surgical team, a dietitian and regular activity matter so much.

Other treatments

Surgery is not the only medical option. Prescription weight-loss medications, including newer injectable drugs, have become much more effective in recent years and can help some people lose a significant amount of weight. Talk to your doctor about which approach, if any, suits your health and goals. For everyday eating and activity, see our pages on weight loss and weight management.

Sources

Last reviewed November 2026. This article is general information, not medical advice.