In an adaptive device and an adaptive method for adapting the stomach opening of a patient, a gastric band having a non-elastic back part on the exterior and a first expandable chamber on the interior are placed around the stomach of the patient for adapting the stomach opening, and the stomach opening of the patient is adapted by modifying the amount of fluid in the first expandable chamber. For this purpose, the adaptive device includes a second expandable chamber, so that the second expandable chamber is connected to the first expandable chamber, and whereby the fluid is displaced from the one expandable chamber to the other expandable chamber in order to modify the stomach opening of the patient. The adaptive device can in particular be controlled by changing the position of the body of the patient.