An artificial stomach for replacing the normal stomach of a patient. The artificial stomach comprising a food reservoir adapted to collect food, an inlet connected to a first opening of the food reservoir and further being adapted to upstream connect to the patient's gastrointestinal tract, and an outlet connected to a second opening of the food reservoir and further being adapted to downstream connect to the patient's gastrointestinal tract. The artificial stomach further comprises an implantable wireless energy receiver configured to receive wireless energy transmitted from a wireless energy transmitter located outside the body of the patient.