Surgery may be an option if you have a body mass index (BMI) of 40 or more. (Use the Interactive Tool: Weight and Health Risks to calculate your BMI.) It may also be an option if you have a BMI of 35 and another health problem related to your weight, such as diabetes or arthritis.

The goal of surgery is to cause significant weight loss. This should reduce obesity-related health problems, including type 2 diabetes and high blood pressure.

It is important to remember that you may still be obese or overweight after the surgery and that surgery will require you to make extreme changes in how you eat, such as eating only a few ounces of food at a time because the surgery creates a much smaller stomach.

Getting good nutrition is also a problem, so you will probably need to take vitamins and supplements. You will also need to avoid high-calorie drinks, which add calories without nutrients.

Two types of surgery are used to treat obesity. A restrictive operation (such as stomach stapling [vertical banded gastroplasty] or adjustable gastric banding) reduces food intake, usually by decreasing the size of the stomach. A malabsorptive, irreversible operation (such as a Roux-en-Y gastric bypass or a biliopancreatic diversion) makes the stomach smaller and decreases the digestion and absorption of food.

Other types of surgery (including intestinal bypass, jaw wiring, and liposuction) have been used to treat obesity. None have been found to have long-term benefit in the treatment of obesity. They are not recommended because of side effects and poor success rates.

Surgery Choices

Restrictive operation (stomach stapling [vertical banded gastroplasty] or gastric banding). In stomach stapling, an incision is made in the abdomen. Surgical staples and a plastic band are used to create a small pouch at the top of the stomach. With gastric banding, a small band is placed around the upper part of the stomach, creating a small pouch.

Roux-en-Y gastric bypass (the most commonly used). Gastric bypass surgery makes the stomach smaller and allows food to bypass part of the small intestine.

Biliopancreatic diversion (rarely used). Biliopancreatic diversion changes the normal process of digestion by making the stomach smaller and allowing food to bypass part of the small intestine so that you absorb fewer calories.

Nutrition concerns

After surgery, you will only be able to eat or drink very small amounts. For the first week or two, you will be on a liquid diet. Once you are able to have solid foods, they will need to be pureed.

You will need to avoid certain foods, depending on which type of surgery you have. Right after surgery, you may not be able to have any liquids that contain sugar, and you may have to avoid milk.