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Bariatric operations can be distinguished into restrictive, malabsorptive or combined. A restrictive operation is one restricting intake, such as a gastric band. Malabdorptive operations primarily reduce the guts ability to absorb nutrients, and an example of this is a Biliopancreatic Diversion. The most common example of a combined operation would be a Roux-en-Y gastric bypass.

In a Roux-en-y gastric bypass, the stomach is divided proximally, creating a small gastric pouch. The jejunum is then divided, and the distal end is brought up to join the gastric pouch, creating a gastrojejunostomy. Food content now passes through the small gastric pouch directly into the jejunum. The remianing proximal free end of the jejunum is then anastamosed to the distal jejunum, creating a jejunojejunostomy. This means the gastric and pancreatic secretions will join the ingested food further down the small bowel. The common limb (where ingested contets and digestive juices travel together) is long, and so this operation is mildly malabsorbative.

In contrast, a much less common operation is the Biliopancreatic Diversion with Duodenal Switch. This is a similar operation to the Roux-en-Y gastric bypass, but it excludes a lot more of the small intestine, meaning its malabsorbative effect is much greater. In this case, the stomach is not divided, but rather a sleeve gastrectomy is performed, where the greater curve is removed, reducing the stomachs overall capacity. This maintains the normal gastric outflow into the duodenum. The proximal duodenum is then divided and connected to the distal jejunum. The biliary-pancreatic limb is now connected to the distal jejunum, but because this is done more distally, the common limb in this operation is very short when compared with a Roux-en-Y bypass, meaning there is a much bigger malabsorbative effect.

Hepaticojejunostomies are where the biliary system is anastamosed to the jejunum to bypass a stricture/injury/malignancy in the distal ducts. A Pancreaticoduodenectomy (Whipple procedure), is often used for removing malignancies in the pancreatic head.