An apparatus for treating obesity of a patient having a stomach with a food cavity. The apparatus comprising a volume filling device adapted to be at least substantially invaginated by a stomach wall portion of the patient with the outer surface of the volume filling device resting against the stomach wall, such that the volume of the food cavity is reduced in size by a volume substantially exceeding the volume of the volume filling device. The apparatus further comprises at least one adjustable stretching device adapted to be at least substantially invaginated by a stomach wall portion of the patient with the outer surface of the stretching device resting against the stomach wall and adapted to stretch a portion of stomach wall, and a fluid connection device interconnecting the volume filling device and the stretching device.
