Abstract: An apparatus for reducing obesity in human beings having an inflatable bag to which a flexible tube is attached. The bag is positioned in the stomach, usually by swallowing, and the tube extends up through the esophagus and out of a nasal cavity or out from the abdomen when a gastrostomy is performed. The bag is inflated by attachment of a supply of fluid to the end of the tube, and then the tube is closed so that the bag will maintain its inflated conditon. With a portion of the open cavity of the patient's stomach occupied by the inflated bag, the patient will sense a feeling of being "filled-up" with only a small amount of food intake.