A gastrointestinal device for treating obesity includes a three-dimensional porous structure configurable between a compressed pre-deployment configuration to facilitate delivery and an expanded post-deployment configuration. The porous structure includes a first opening at its proximal end and a larger second opening at its distal end. The porous structure also includes a sleeve coupled to its distal end. Optionally, the device further includes a suture at the proximal end of the wire mesh structure to facilitate retrieval and an anti-migration component positioned at the junction of the porous structure with the sleeve. The porous structure is deployed in a patient's stomach such that the anti-migration component sits proximal to the patient's pylorus and prevents migration of the entirety of the device into and through the pylorus. The sleeve extends through the pylorus, into the duodenum and ends in the duodenum or jejunum. Food enters the device from the first opening at the proximal end of the porous structure, passes through the porous structure and sleeve, and exits at the distal end of the sleeve. The device treats obesity by providing a relatively immovable volume occupying structure in the stomach and a bypass for food past the pylorus and proximal portion of the small intestine. Optionally, the device further acts to slow the passage of food through the digestive tract. Patients with the device experience satiety more quickly and have a prolonged sensation of satiety.