Surgeries for weight loss can be restrictive or a combination of restrictive and malabsorptive.

• Restrictive: This type of surgery makes the stomach smaller. It limits the amount of food the stomach can hold.
• Malabsorptive: This surgery changes the path of the intestine. Food goes around (or bypasses) part of the intestine. Since nutrients are normally absorbed in the intestine, bypassing a part of it reduces how much it can absorb. This can lead to weight loss.

Examples of restrictive surgeries include:

• Adjustable gastric banding . A band is placed around the upper part of the stomach, creating a pouch. The band is adjustable, so the size of the opening between the pouch and the stomach can be adjusted.
• Gastric sleeve. More than half of your stomach is removed, leaving a thin sleeve, or tube, that is about the size of a banana. Because part of your stomach has been removed, this surgery can't be reversed.

Examples of restrictive and malabsorptive combined include:

• Roux-en-Y gastric bypass . A small part of the stomach is used to create a new stomach pouch, roughly the size of an egg. The smaller stomach is connected to the middle portion of the small intestine, bypassing the rest of the stomach and the upper portion of the small intestine. This reduces the amount of food you can eat at one time. Bypassing part of the intestine reduces how much food and nutrients are absorbed. This leads to weight loss.
• Biliopancreatic diversion.This surgery changes the normal process of digestion by making the stomach smaller. It allows food to bypass part of the small intestine so that you absorb fewer calories. There are two biliopancreatic diversion surgeries:
  • In a biliopancreatic diversion, part of the stomach is removed. The remaining part of the stomach is connected to the lower part of the small intestine. The food you eat then bypasses much of the small intestine. This results in fewer calories absorbed and weight loss.
  • In a biliopancreatic diversion with duodenal switch, a portion of the stomach is removed, but the pylorus remains intact. The pylorus controls food drainage from the stomach. The pylorus is connected to a lower segment of the intestine. The duodenum is connected to the lower part of the small intestine. The food you eat then bypasses much of the small intestine. This results in fewer calories absorbed and weight loss.

Two ways surgery is done

• Open surgery. The surgeon makes a large cut in the belly.
• Laparoscopic surgery. The surgeon makes several small cuts and uses small tools and a camera to guide the surgery. You recover sooner and may be less likely to have pain or problems after surgery. This is the type of surgery done most often for weight loss.

After surgery, you'll need to make lifelong changes in how you eat and drink.

• Eat small meals. You can eat only a few ounces of food at a time. Your new stomach will hold only a tiny amount of food.
• Eat slowly. You must eat very slowly and chew your food to mush. Otherwise, you may vomit often and have pain.
• Don't drink liquids with meals. You won't be able to drink for 30 minutes before you eat, during your meal, and for 30 minutes after you eat. There won't be room in your stomach for both drinks and solid food.
• Use alcohol with care. Be careful about drinking alcohol. After gastric bypass or gastric sleeve surgery, you may become intoxicated much more quickly. Alcohol also can cause ulcers in your stomach and intestines.
• Take vitamins as recommended. You will need to take vitamins and supplements, because you won't get enough nutrition from the small amounts of food you eat. If you have surgical changes to your intestines, your body won't absorb all the nutrition from the food.
• Avoid fatty, sugary foods. You may have to avoid foods that contain simple sugars—like candy, juices, ice cream, condiments, and soft drinks. Simple sugars may cause a problem called dumping syndrome. This happens because food moves too quickly through the stomach and intestines. It can cause shaking, sweating, dizziness, rapid heart rate, and often severe diarrhea. It can also cause belly pain, cramping, and nausea. Dumping syndrome may occur after gastric bypass surgery, but is unlikely after gastric band or gastric sleeve surgery.

People who are very overweight are more likely than other people to have problems from any kind of surgery.

After any weight-loss surgery

• You could get an infection in the area where cuts were made.
• A blood clot can form and block blood flow in the lung (pulmonary embolism).
• You may not get enough of certain vitamins and minerals. This can lead to problems such as anemia and osteoporosis.
• Some people get gallstones.
• You may gain the weight back a few years after surgery if you don't follow your eating and lifestyle plan.
• There is a risk of death. This is a risk of any surgery.

Risks of each surgery

Each type of surgery also has its own risks. Here are a few examples:

• Gastric bypass and gastric sleeve surgeries can cause a leak from the stomach into the belly area. The leak can cause an infection called peritonitis.
• With gastric bypass, the connection between the stomach and the small intestine can get narrow. This can cause nausea and vomiting after eating.
• After adjustable gastric banding, you are more likely to need another surgery to fix problems than you would after gastric bypass. For example, some people need a second operation because the band slips or it works its way from the outside of the stomach to the inside. This is called an erosion.

Extra skin after weight loss

Weight-loss surgery is not cosmetic surgery. It will not remove fatty tissue. And after a lot of weight loss, you may have excess skin. Some people choose to have more surgery to remove skin from the belly, thighs, upper arms, or breasts.

Your doctor may recommend weight-loss surgery if:

• Your BMI is at least 40 (or your BMI is at least 35 and you have other health problems related to your weight).
• You have tried for at least 6 months to lose weight with diet and exercise.
• You do not abuse alcohol.
• You do not have untreated depression or another major mental illness.

Weight-loss surgery for teens

Most people who have weight-loss surgery are 18 to 65 years old. It is sometimes done on people younger than 18.

In adolescents, as in adults, these types of surgery are not usually suggested unless the child's BMI is over 40 or the child has severe health problems and a BMI over 35.

Younger children may not be considered for surgery unless their BMI is even higher. Your child's doctor can help you decide if the health risks of severe obesity outweigh the risks of surgery. Surgery is considered only after changes have been made to increase physical activity, eat the right range of calories, and possibly use medicine for weight loss, under the direction of a doctor.