An implantable device including a supporting member, such as a ring, or series of rings, and an impeding member that is used to adjust the effective area of the created orifice after implantation. The rings may hold pleats of gastric tissue in place around their circumference to create a reinforced constriction within an organ. The rings may be attached to one another with folds or pleats of tissue held between them. If the organ is a stomach, the constriction is positioned such that a chamber of a predetermined volume is created proximal to the constriction, leaving a narrow opening or stoma to the remainder of the stomach's volume distal to the constriction. At least one of the rings is adapted to have an impeding member that may be endoscopically adjusted in order to alter the size of the effective orifice area of the opening or outlet. The occluding member may be a ball suspended by a suspension line connected to opposing sides of the supporting member.