What to Expect

About Gastric Bypass Surgery

There have been many operations done over the past forty years to assist patients in controlling their weight. Some have proven to be more effective than others, and some have more side effects. Today in the United States, the two most commonly performed operations are gastric bypass surgery and the vertical banded gastroplasty. Most bariatric surgeons now exclusively perform the gastric bypass surgery because it has proven, in the long term, to provide greater weight loss with minimal side effects.

The gastric bypass surgery has been performed with minor variations since 1968. It has been shown to be effective in controlling morbid obesity in the long term.

The gastric bypass operation is designed to limit the amount of food you eat. This is done by stapling and dividing the stomach. The “new stomach”, also called the pouch, is only about 5–10% the size of the “old stomach” and holds less food. The pouch is about the size of a golf ball as opposed to a normal stomach, which is about the size of a football. The pouch is designed to be permanent, although it is reversible.

When food enters the pouch, it must have a way to leave. An opening is made from the pouch to the small intestine. This opening is called a stoma and is about the size of a dime. The opening is made small so that food empties slowly and the sensation of being full or satisfied lasts longer. Because the opening leaving the pouch is small, you must cut your food into small pieces and chew it well for food to be able to pass easily. It is possible to damage the pouch and stoma by overeating. This could result in stretching the pouch and dilating the stoma. If this occurs, your weight loss and long term results will not be as good.

A type of intestinal connection is created, called a Roux–en–Y. The part of the small intestine that is attached to the pouch does not metabolize refined sugars well. Approximately 50% of people who undergo this operation may have difficulty with foods or liquids high in refined sugar (table sugar). If you are one of these people, after the operation if you consume a large amount of refined sugar (chocolate bar/cheesecake/syrup), you may not feel well for 5–20 minutes. When large amounts of sugar enter the pouch attached to the intestine, a signal goes to the pancreas to secrete insulin. Insulin lowers your blood sugar and this can give patients what is called “dumping syndrome.” Symptoms may include a cold sweat, an ill stomach, and/or possible diarrhea. In general, this is unpleasant and people would not intentionally experience it again. This mechanism assists in keeping patients from consuming large amounts of calorie rich sugar and helps in weight reduction. The normal amount of sugar in what is not considered desserts or snack food will generally not cause these symptoms.

The bottom part of the stomach is not removed and continues to function. The bottom part of the stomach will secrete the gastric juices as before and they empty into the small intestine to mix with the food and assist in digestion.

The three mechanisms by which patients lose weight after the gastric bypass surgery are:

1. The pouch is very small and holds only a tiny portion of food. You feel full quickly.
2. The size of the opening, called the stoma, allows food to empty only slowly from the pouch. You stay full for a long period of time after consuming small amounts of food.
3. A large number of patients have the inability to tolerate large amounts of refined sugar.