Implants for treatment of obesity may be placed within the stomach and/or esophagus or around the outside surface of the stomach and/or esophagus. The implants comprise at least a portion constructed of a shape memory material. The implants are thus adapted to be implanted in a deformed shape, and then to be transformed through the application of activation energy into a memorized shape. The shape and/or size transformation induces a change in shape of the stomach and/or esophagus, thus altering the normal digestive path of food entering the patient's gastrointestinal tract.