Bariatric surgery operations are classified by the mechanism by which they help to lose weight. They can either decrease the capacity of stomach and hence restrict food intake (restrictive procedures) or reduce the effective length of the intestine to decrease the absorption of food (malabsorptive procedures) or work by both mechanisms (combined procedures).
Restrictive procedures include
- Sleeve gastrectomy– The operation removes around 80% of the stomach using a specialized laparoscopic stapling gun. This staples the stomach on both sides and cuts in between which makes the procedure fast and bloodless. The volume of the stomach is reduced from initial 2000 cc to only 150 -200 cc. This markedly reduces the amount of food that can be consumed at one sitting.
Also, removal of the stomach reduces the level of hunger hormone (ghrelin). This makes the person satiated early and helps in weight loss. The 5 year expected excess weight loss for this procedure is up to 70%.
- Adjustable Gastric banding– In this procedure, an adjustable silicon band is placed around the upper end of the stomach which helps to regulate food intake and provide a sense of satiety to the patient. There is no cutting of stomach or bypass of the intestine which makes it one of the fastest and safest bariatric procedures to perform. The amount of fluid which is present within the band can adjusted from an access port placed under the skin which can tighten or loosen the band and regulate weight loss.
- Gastric plication– This is a novel bariatric procedure wherein a part of the stomach is sewn with non-absorbable sutures to reduce its size. The shape and volume of the stomach becomes similar to that seen after sleeve gastrectomy. However, this is an economical option for patients who cannot afford the previously mentioned procedures since stapling guns and cartridges which increase the cost of a procedure are not used in this procedure
Combined procedures include
- Roux en Y gastric bypass-. It is regarded as the gold standard bariatric procedure and was the most commonly performed bariatric surgery until recently sleeve gastrectomy took this place. In this procedure, the upper part of the stomach is converted into a small pouch to restrict intake andis connected directly to the mid part of the small intestine. This new anatomy bypasses the lower part of stomach and the first part of the small intestine which delays the mixing of food with the digestive enzymes and hence results in malabsorption.
The combined effect of restriction and malabsorption results in rapid and sustained weight loss. The direct contact of food with the small intestine results in release of hormones which increase the metabolic rate and burn fat. This not only decreases body weight but also helps in remission of metabolic diseases like diabetes and hyperlipidemia.
- Mini – It is combined procedure in which a long narrow gastric tube is created and joined directly to the mid portion of the small intestine. It differs from the classical RYGB in the size of the gastric pouch which is considerably larger and the diameter of the anastomosis between the pouch and the intestine which is also wider. As a result, the patient is able to eat larger portions of food than that possible after a RYGB. The main mechanism by which this procedure works is malabsorption due to delay in the mixing of food and digestive enzymes. It also results in effective excess weight loss of up to 80% with remission of comorbid diseases.
- Bilio pancreatic diversion with Duodenal Switch– It is a combined procedure which involves creating a tube of the stomach like that for a sleeve gastrectomy and bypassing around two thirds of the total length of the intestine for malabsorption. Although still being done widely in the western world, it has not gained popularity in Asia because of the malabsorptive side effects leading to diarrhea and protein malnutrition particularly when diet is deficient in protein. It leads to 80-90% of excess weight loss with excellent resolution of comorbid illnesses.
Malabsortive procedures include
- Jejunoileal bypass – It is purely a malabsorptive procedure which connects the proximal part to the small intestine to the terminal ileum decreasing the effective length for absorption of food. This procedure is not performed these days due to its side effects.