According to the American Society for Metabolic & Bariatric Surgery (ASMBS) and the National Institutes of Health, Roux-en-Y gastric bypass is the current gold standard procedure for weight loss surgery. It is the most frequently performed operation for weight loss in the United States, accounting for more than 90% of all weight loss surgeries.

In the Roux-en-Y gastric bypass procedures, a surgeon makes a direct connection from the stomach to a lower segment of the small intestine, bypassing the duodenum, and some of the jejunum. A 15 - 60 cc proximal gastric pouch is created using several staple lines. The proximal gastric pouch is drained into a segment of the jejunum and "bypasses" the distal stomach and duodenum. The proximal part of the divided intestine is then connected to the side of the intestine that was previously attached to the pouch. The roux limb is that part of the intestine between the stomach pouch and the connection to the proximal small intestine.

The result is a sustained weight loss of >50% excess body weight in over 80% of patients. The surgery can be done laparoscopically or open. This procedure may be an option for people with a BMI between 35 and 40 who suffer from life-threatening problems for example, severe sleep apnea or obesity-related heart disease or diabetes.

A Gastric Band (lap band) surgical procedure is a purely restrictive approach to reducing the capacity of the stomach by which a band is placed around the upper most part of the stomach giving it the shape of an hour glass. This band divides the stomach into two portions, one small and one larger portion. No stomach stapling is required. The gastric band induces an early feeling of stomach fullness, thereby decreasing food intake. Your digestive system is not altered in any way.

Weight reduction will instead be achieved by the fact that you will simply feel the need to eat less.

Duodenal switch combines two surgical techniques: restrictive and malabsorptive.

The restrictive component reduces the size of the stomach. Your surgeon divides the stomach vertically and removes 75 percent of it. The remaining stomach is banana shaped and about 6 ounces in size.

Duodenal switch leaves the pyloric valve intact, which regulates the release of stomach contents into the small intestine. It also keeps a small part of the duodenum in the digestive system. Foods mixes with stomach acid, then moves into the duodenum, where its mixed with bile from the gall bladder and digestive juices from the pancreas.

The malabsorptive component of duodenal switch surgery involves rearranging the small intestine to separate the flow of food from the flow of bile and pancreatic juices. The food and digestive juices interact only in the last 18 to 24 inches of the intestine, allowing for malabsorption.