Obesity and Gastrointestinal Surgery

by National Institute of Health

Severe obesity is a chronic condition that is difficult to treat through diet and exercise alone. Gastrointestinal surgery is an option for people who are severely obese and cannot lose weight by traditional means or who suffer from serious obesity-related health problems. The operation promotes weight loss by restricting food intake and, in some operations, interrupting the digestive process. As in other treatments for obesity, the best results are achieved with healthy eating behaviors and regular physical activity.

You may be a candidate for surgery if you have:

1. a body mass index (BMI) of 40 or more - about 100 pounds overweight for men and 80 pounds for women.

2. a BMI between 35 and 39.9 and a serious obesity-related health problem such as type 2 diabetes, heart disease, or severe sleep apnea (when breathing stops for short periods during sleep).

3. an understanding of the operation and the lifestyle changes you will need to make.

The Normal Digestive Process

Normally, as food moves along the digestive tract, digestive juices and enzymes digest and absorb calories and nutrients (see figure 1). 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 juice 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 until eliminated.

How Does Surgery Promote Weight Loss?

Gastrointestinal surgery for obesity, also called bariatric surgery, alters the digestive process. The operations can be divided into three types: restrictive, malabsorptive, and combined restrictive/malabsorptive. Restrictive operations limit food intake by creating a narrow passage from the upper part of the stomach into the larger lower part, reducing the amount of food the stomach can hold and slowing the passage of food through the stomach. Malabsorptive operations do not limit food intake, but instead exclude most of the small intestine from the digestive tract so fewer calories and nutrients are absorbed. Malabsorptive operations, also called intestinal bypasses, are no longer recommended because they result in severe nutritional deficiencies. Combined operations use stomach restriction and a partial bypass of the small intestine.

What Are the Surgical Options?

Malabsorptive operations, also called intestinal bypasses, are no longer recommended because they result in severe nutritional deficiencies.

There are several types of restrictive and combined operations. Each one has its own benefits and risks.

Restrictive Operations

Purely restrictive operations only limit food intake and do not interfere with the normal digestive process. To perform the operation, doctors create a small pouch at the top of the stomach where food enters from the esophagus. At first, the pouch holds about 1 ounce of food and later may stretch to 2-3 ounces. The lower outlet of the pouch is usually about ½ inch in diameter or smaller. This small outlet delays the emptying of food from the pouch into the larger part of the stomach and causes a feeling of fullness. After the operation, patients can no longer eat large amounts of food at one time. Most patients can eat about ½ to 1 cup of food without discomfort or nausea, but the food has to be soft, moist, and well chewed. Patients who undergo restrictive procedures generally are not able to eat as much as those who have combined operations.

Purely restrictive operations for obesity include adjustable gastric banding (AGB) and vertical banded gastroplasty (VBG).

1. Adjustable gastric banding. In this procedure, a hollow band made of silicone rubber is placed around the stomach near its upper end, creating a small pouch and a narrow passage into the rest of the stomach (figure 2). The band is then inflated with a salt solution through a tube that connects the band to an access port placed under the skin. It can be tightened or loosened over time to change the size of the passage by increasing or decreasing the amount of salt solution.

2. Vertical banded gastroplasty. VBG uses both a band and staples to create a small stomach pouch, as illustrated in figure 3. Once the most common restrictive operation, VBG is not often used today.

Advantages: Restrictive operations are easier to perform and are generally safer than malabsorptive operations. AGB is usually done via laparoscopy, which uses smaller incisions, creates less tissue damage, and involves shorter operating time and hospital stays than open procedures. (See below for more information on laparoscopy.) Restrictive operations can be reversed if necessary, and result in few nutritional deficiencies.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.