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An Overview of Weight Loss Surgery

Severe obesity is a chronic condition that is very difficult to treat. For some people, weight loss surgery -- or bariatric surgery -- helps by restricting food intake or interrupting digestive processes. But keep in mind that weight loss surgery is a serious undertaking. You should clearly understand the pros and cons associated with the procedures before making a decision.

In order to understand how weight loss works, you need to first understand how the normal digestive process functions.

Normally, as food moves along the digestive tract, appropriate digestive juices and enzymes arrive at the right place and at the right time to digest and absorb calories and nutrients. After we chew and swallow our food, it moves down the esophagus to the stomach, where a strong acid continues the digestive process. The stomach can hold about 3 pints of food at one time. When the stomach contents move to the duodenum, the first segment of the small intestine, bile and pancreatic juices speed up digestion. Most of the iron and calcium in the foods we eat is absorbed in the duodenum. The jejunum and ileum, the remaining two segments of the nearly 20 feet of small intestine, complete the absorption of almost all calories and nutrients. The food particles that cannot be digested in the small intestine are stored in the large intestine (made up of the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum) until eliminated.

Obesity surgery involves making changes to the stomach and/or small intestine.

How Does Weight Loss Surgery Work?

The concept of gastric surgery to control obesity grew out of results of operations for cancer or severe ulcers that removed large portions of the stomach or small intestine.

Because patients undergoing these procedures tended to lose weight after surgery, some doctors began to use such operations to treat severe obesity. The first operation that was widely used for severe obesity was a type of intestinal bypass. This operation, first used 40 years ago, caused weight loss through malabsorption (decreased ability to absorb nutrients from food because the intestines were removed or bypassed).

The idea was that patients could eat large amounts of food, which would be poorly digested or passed along too fast for the body to absorb many calories. The problem with this surgery was that it caused a loss of essential nutrients (malnutrition) and its side effects were unpredictable and sometimes fatal. The original form of the intestinal bypass operation is no longer used.

Surgeons now use other techniques that produce weight loss primarily by limiting how much the stomach can hold. Two types of surgical procedures used to promote weight loss are:

  • Restrictive surgery: During these procedures the stomach is made smaller. A section of your stomach is removed or closed, which limits the amount of food it can hold and causes you to feel full.
  • Malabsorptive surgery: Most of digestion and absorption takes place in the small intestine. Surgery to this area shortens the length of the small intestine and/or changes where it connects to the stomach, limiting the amount of food that is completely digested or absorbed (causing malabsorption). These surgeries are now performed along with restrictive surgery.

Through food intake restriction, malabsorption, or a combination of both, you can lose weight since less food either goes into your stomach or stays in your small intestine long enough to be digested and absorbed.

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