Described here are devices and methods for intussuscepting a portion of stomach tissue. Typically the intussusception is created at a position near, but distal to the gastroesophageal junction, and a pouch capable of storing a volume (from about 0 cc up to about 100 cc) is created proximal the intussuscepted tissue. In this way, the amount of food that may be ingested is reduced, helping to ameliorate GERD symptoms, and aiding in weight loss efforts. Some of the devices described here include an expandable member and at least one suction inlet. In these devices, the expandable member is expanded to create a proximal cavity into which the stomach tissue is pulled (e.g., using suction), thereby creating the intussusception.