If a person embarks on a hunger strike or just stops eating for whatever reason, either a medical reason or because they decide to exercise their right to withdraw treatment, they have that right. A person has the right to say, “I do not want any food or liquid from this point on. I do want any medication.” They have the legal right to do that.
At some point after they make that decision, a doctor can say that this person's death is reasonably foreseeable. They don't have to die of starvation, because at that point in time a A doctor can say that this person is going to die a natural death as a result of malnourishment, and that they therefore may qualify. Of course, that's not the only condition they must have; they have to meet all the other four or five conditions.