A self-regulating gastric band apparatus for adjusting stoma size is disclosed. The apparatus includes an adjustable gastric band that has an expandable portion containing a volume of fluid. A band adjustment assembly is provided for implanting with the gastric band that includes a sensor for sensing fluid pressure in the expandable portion. The band adjustment assembly further includes a pump assembly connected to the expandable portion and to a controller that can operate the pump assembly to adjust the volume of the fluid in the band based on the sensed fluid pressure. The band adjustment assembly includes memory storing an operating range relative to a target fluid pressure, and the pump assembly is operated to maintain the sensed band pressure within the operating range. The target pressure is set to maintain pressure variations below a predefined variation limit generally corresponding with satiated fill volumes for a particular patient and implanted band.