The Gastric Bypass

Gastric bypass surgery is one type of procedure that can be used to cause significant weight loss if you are very obese. The surgery reduces your body's intake of calories. Calorie reduction is accomplished in two ways:

1. After the surgery, your stomach is smaller. You feel full faster and learn to reduce the amount that you eat at any given time.
2. Part of your stomach and small intestines are literally bypassed (skipped over) so that fewer calories are absorbed. Unfortunately, sometimes nutrients are lost as well.

What Types of Gastric Bypass Operations Are There?

• Roux-en-Y gastric bypass (RGB). This operation is the most common gastric bypass procedure performed. First, a small stomach pouch is created by stapling part of the stomach together or by vertical banding. This limits how much food you can eat. Next, a Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the duodenum as well as the first portion of the jejunum. This causes reduced calorie and nutrient absorption.

Extensive gastric bypass (biliopancreatic diversion). In this more complicated gastric bypass operation, portions of the stomach are removed. The small pouch that remains is connected directly to the final segment of the small intestine, thus completely bypassing both the duodenum and jejunum. Although this procedure successfully promotes weight loss, it is not widely used because of the high risk for nutritional deficiencies.

Gastric bypass operations that cause malabsorption and restrict food intake produce more weight loss than restriction operations, which only decrease food intake. People who have bypass operations generally lose two-thirds of their excess weight within 2 years.

Are There Risks Associated With Gastric Bypass Surgery?

Yes. People who undergo this procedure are at risk for:

• Pouch stretching (stomach gets bigger overtime, stretching back to its normal size before surgery).
• Leakage of stomach contents into the abdomen.
• Nutritional deficiencies causing health problems.

Gastric bypass operations also may cause "dumping syndrome," whereby stomach contents move too rapidly through the small intestine. Symptoms include nausea, weakness, sweating, faintness, and, occasionally, diarrhea after eating, as well as the inability to eat sweets without becoming extremely weak.

What Health Problems Can Nutritional Deficiencies Cause?

The limited absorption of vitamin B12 and iron can cause anemia. The lack of calcium absorption can cause osteoporosis and metabolic bone disease. People who undergo this procedure are required to take nutritional supplements that usually prevent these deficiencies.

The more extensive the bypass operation, the greater is the risk for complications and nutritional deficiencies. People who undergo extensive bypasses of the normal digestive process require not only close monitoring, but also life-long use of special foods and medications.