A device (10) for treatment of obesity of a patient comprises an annular element (12) having a relatively large outer boundary and a relatively small inner boundary, and an elongated flexible tube (14) extending from the relatively small inner boundary of the annular element to a distal end. The relatively large outer boundary is adapted to be attached to an inner wall of a stomach (100) of a patient, such that the annular element divides the stomach (100) into two chambers, an esophagus-end chamber close to an esophagus of the patient, and a pylorus-end chamber close to a pylorus of the patient. The invention also provides a method for treatment of obesity of a patient which includes inserting an annular element having a relatively large outer boundary and a relatively small inner boundary into a stomach of the patient, and attaching the relatively large outer boundary of the annular element to an inner circumference of the stomach of the patient.