Method and apparatus for limiting absorption of food products in specific parts of the digestive system is presented. A gastrointestinal implant device is anchored in the duodenum and extends beyond the ligament of Treitz. All food exiting the stomach is funneled through the device. The gastrointestinal device includes an anchor for attaching the device to the duodenum and an unsupported flexible sleeve to limit absorption of nutrients in the duodenum. The anchor can include a stent and/or a wave anchor and is collapsible for catheter-based delivery and removal.