A collapsible gastrointestinal anchor can be characterized in various embodiments by a radial force of about 0.1 Newtons (N) or greater at a compressed diameter of 25 millimeters (mm); by an average spring rate of about 13 Newtons/meter (N/m) or greater in a range of motion between a relaxed diameter and a compressive elastic deformation diameter; or by a radial force over the range of motion of about 0.1 N or greater. Typically, the anchor can be adapted to be retained within a subject's intestine, more typically in the duodenum, or particularly in the duodenal bulb just distal to the pylorus. A gastrointestinal implant device includes the collapsible gastrointestinal anchor and a floppy sleeve. The sleeve is open at both ends and adapted to extend into a subject's intestine, the anchor being coupled to a proximal portion of the sleeve. Also include are methods of implanting the gastrointestinal implant device in a subject, and methods of treating a subject for disease. The disclosed gastrointestinal invention leads to an improved ability to secure anchors and devices in the gastrointestinal tract while tending to minimize migration.