Gastric bypass procedures (GBP) are any of a group of similar operations used to treat morbid obesity—the severe accumulation of excess weight as fatty tissue—and the health problems (comorbidities) it causes. Bariatric surgery is the term encompassing all of the surgical treatments for morbid obesity, not just gastric bypasses, which make up only one class of such operations.

A gastric bypass first divides the stomach into a small upper pouch and a much larger, lower "remnant" pouch and then re-arranges the small intestine to allow both pouches