1. Restrictive procedures that decrease food intake.
2. Malabsorptive procedures that alter digestion, thus causing the food to be poorly digested and incompletely absorbed so that it is eliminated in the stool.

Gastric Restrictive Procedure - Vertical Banded Gastroplasty
Malabsorptive Procedures - Biliopancreatic Diversion
Proximal Gastric Bypass - Roux-en-Y
Revisional Bariatric Surgery

Gastric Restrictive Procedure - Vertical Banded Gastroplasty 
Vertical Banded Gastroplasty (VBG) is a purely restrictive procedure. In this procedure the upper stomach near the esophagus is stapled vertically for about 2-1/2 inches (6 cm) to create a smaller stomach pouch. The outlet from the pouch is restricted by a band or ring that slows the emptying of the food and thus creates the feeling of fullness.

Advantages

• The primary advantage of this restrictive procedure is that a reduced amount of well-chewed food enters and passes through the digestive tract in the usual order. That allows the nutrients and vitamins (as well as the calories) to be fully absorbed into the body.
• After 10 years, studies show that patients can maintain 50% of targeted excess weight loss.

• Postoperatively, stapling of the stomach carries with it the risk of staple-line disruption that can result in leakage and/or serious infection. This may require prolonged hospitalization with antibiotic treatment and/or additional operations.
• Staple-line disruption may also, in the long-term, lead to weight gain. For these reasons, some surgeons divide the staple-line wall of the pouch from the rest of the stomach to reduce the risk of long-term staple-line disruption.
• The band or ring applied may lead to complications of obstruction or perforation, requiring surgical intervention.
• Characteristically, these procedures, while creating a sense of fullness, do not provide the necessary feeling of satisfaction that one has had "enough" to eat.
• Because restrictive procedures rely solely on a small stomach pouch to reduce food intake, there is the risk of the pouch stretching or of the restricting band or ring at the pouch outlet breaking or migrating, thus allowing patients to eat too much.
• Around 40% of patients undergoing these procedures have lost less than half their excess body weight.
• As is the case with all weight loss surgeries, readmission to a hospital may be required for fluid replacement or nutritional support if there is excessive vomiting and adequate food intake cannot be maintained.

Malabsorptive Procedures - Biliopancreatic Diversion 
While these operations also reduce the size of the stomach, the stomach pouch created is much larger than with other procedures. The goal is to restrict the amount of food consumed and alter the normal digestive process, but to a much greater degree. The anatomy of the small intestine is changed to divert the bile and pancreatic juices so they meet the ingested food closer to the middle or the end of the small intestine.With the three approaches discussed below, absorption of nutrients and calories is also reduced, but to a much greater degree than with previously discussed procedures. Each of the three differs in how and when the digestive juices (i.e., bile) come into contact with the food.

Since food bypasses the duodenum, all the risk considerations discussed in the gastric bypass section regarding the malabsorption of some minerals and vitamins also apply to these techniques, only to a greater degree.

Biliopancreatic Diversion (BPD) 
BPD removes approximately 3/4 of the stomach to produce both restriction of food intake and reduction of acid output. Leaving enough upper stomach is important to maintain proper nutrition. The small intestine is then divided with one end attached to the stomach pouch to create what is called an "alimentary limb." All the food moves through this segment, however, not much is absorbed. The bile and pancreatic juices move through the "biliopancreatic limb," which is connected to the side of the intestine close to the end. This supplies digestive juices in the section of the intestine now called the "common limb." The surgeon is able to vary the length of the common limb to regulate the amount of absorption of protein, fat and fat-soluble vitamins.

Extended (Distal) Roux-en-Y Gastric Bypass (RYGBP-E) 
RYGBP-E is an alternative means of achieving malabsorption by creating a stapled or divided small gastric pouch, leaving the remainder of stomach in place. A long limb of the small intestine is attached to the stomach to divert the bile and pancreatic juices. This procedure carries with it fewer operative risks by avoiding removal of the lower 3/4 of the stomach. Gastric pouch size and the length of the bypassed intestine determine the risks for ulcers, malnutrition and other effects.

Biliopancreatic Diversion with "Duodenal Switch" 
This procedure is a variation of BPD in which stomach removal is restricted to the outer margin, leaving a sleeve of stomach with the pylorus and the beginning of the duodenum at its end. The duodenum, the first portion of the small intestine, is divided so that pancreatic and bile drainage is bypassed. The near end of the "alimentary limb" is then attached to the beginning of the duodenum, while the "common limb" is created in the same way as described above.

Advantages

1. These operations often result in a high degree of patient satisfaction because patients are able to eat larger meals than with a purely restrictive or standard Roux-en-Y gastric bypass procedure.
2. These procedures can produce the greatest excess weight loss because they provide the highest levels of malabsorption.
3. In one study of 125 patients, excess weight loss of 74% at one year, 78% at two years, 81% at three years, 84% at four years, and 91% at five years was achieved.
4. Long-term maintenance of excess body weight loss can be successful if the patient adapts and adheres to a straightforward dietary, supplement, exercise and behavioral regimen.

1. For all malabsorption procedures there is a period of intestinal adaptation when bowel movements can be very liquid and frequent. This condition may lessen over time, but may be a permanent lifelong occurrence.
2. Abdominal bloating and malodorous stool or gas may occur.
3. Close lifelong monitoring for protein malnutrition, anemia and bone disease is recommended. As well, lifelong vitamin supplementing is required. It has been generally observed that if eating and vitamin supplement instructions are not rigorously followed, at least 25% of patients will develop problems that require treatment.
4. Changes to the intestinal structure can result in the increased risk of gallstone formation and the need for removal of the gallbladder.
5. Re-routing of bile, pancreatic and other digestive juices beyond the stomach can cause intestinal irritation and ulcers.

Proximal Gastric Bypass
Roux-en-Y
In recent years, better clinical understanding of procedures combining restrictive and malabsorptive approaches has increased the choices of effective weight loss surgery for thousands of patients. By adding malabsorption, food is delayed in mixing with bile and pancreatic juices that aid in the absorption of nutrients. The result is an early sense of fullness, combined with a sense of satisfaction that reduces the desire to eat.

According to the American Society for Bariatric Surgery and the National Institutes of Health, Roux-en-Y gastric bypass is the current gold standard procedure for weight loss surgery. It is one of the most frequently performed weight loss procedures in the United States. In this procedure, stapling creates a small (15 to 20cc) stomach pouch. The remainder of the stomach is not removed, but is completely stapled shut and divided from the stomach pouch. The outlet from this newly formed pouch empties directly into the lower portion of the jejunum, thus bypassing calorie absorption. This is done by dividing the small intestine just beyond the duodenum for the purpose of bringing it up and constructing a connection with the newly formed stomach pouch. The other end is connected into the side of the Roux limb of the intestine creating the "Y" shape that gives the technique its name. The length of either segment of the intestine can be increased to produce lower or higher levels of malabsorption.

Advantages

• The average excess weight loss after the Roux-en-Y procedure is generally higher in a compliant patient than with purely restrictive procedures.
• One year after surgery, weight loss can average 77% of excess body weight.
• Studies show that after 10 to 14 years, 50-60% of excess body weight loss has been maintained by some patients.
• A 2000 study of 500 patients showed that 96% of certain associated health conditions studied (back pain, sleep apnea, high blood pressure, diabetes and depression) were improved or resolved.

• Because the duodenum is bypassed, poor absorption of iron and calcium can result in the lowering of total body iron and a predisposition to iron deficiency anemia. This is a particular concern for patients who experience chronic blood loss during excessive menstrual flow or bleeding hemorrhoids. Women, already at risk for osteoporosis that can occur after menopause, should be aware of the potential for heightened bone calcium loss.
• Bypassing the duodenum has caused metabolic bone disease in some patients, resulting in bone pain, loss of height, humped back and fractures of the ribs and hip bones. All of the deficiencies mentioned above, however, can be managed through proper diet and vitamin supplements.
• A chronic anemia due to Vitamin B12 deficiency may occur. The problem can usually be managed with Vitamin B12 pills or injections.
• A condition known as "dumping syndrome " can occur as the result of rapid emptying of stomach contents into the small intestine. This is sometimes triggered when too much sugar or large amounts of food are consumed. While generally not considered to be a serious risk to your health, the results can be extremely unpleasant and can include nausea, weakness, sweating, faintness and, on occasion, diarrhea after eating. Some patients are unable to eat any form of sweets after surgery.
• In some cases, the effectiveness of the procedure may be reduced if the stomach pouch is stretched and/or if it is initially left larger than 15-30cc.
• The bypassed portion of the stomach, duodenum and segments of the small intestine cannot be easily visualized using X-ray or endoscopy if problems such as ulcers, bleeding or malignancy should occur.