An implantable device intended to be swallowed or endoscopically inserted into the stomach where it is inflated to reduce stomach volume and facilitate weight loss in overweight/obese patients by restricting the quantity of food consumed through an increased sense of satiety (fullness). It is designed to be inflated/filled with an inert material (e.g., saline, air, nitrogen) in situ, where it remains until it is endoscopically removed or deflates and passes through the bowels. Disposable devices dedicated to introduction/inflation may be included with the balloon.