The weight contract in hospital treatment of mental anorexia, first inscribes in the heads of the patient and her family the disavowal of concern for somatic reality and its outcome, at risk of grave complications. Then it quickly becomes clear that the question is not the fantasized one of « force feeding » through a medical technique that will make her fat, but that of the process of becoming a woman, hampered by the girl who actively and willingly aborts her adolescent process. This symbolic effect of the contract has effects on the body and thought processes of the patient, allowing for revision of identifications. The constraint experienced in the therapeutic act is always much less than the violence of primitive relations of the subject of the ego with its archaic superego and aims to ease the interior constraints at the origin of food restriction and weight loss. « External » persecution opposes an internal dictator … the conflict is displaced onto the relation with the treatment (which figures the conflicts with the parents) and allows for the emergence of new possibilities of representation. The conflict is human again and for a while disavowal, splitting and projection will occur, as defenses, before the encounter within the conflict becomes possible, an encounter which protects the patient’s narcissism (she is not humiliated by asking for help, the bond having been imposed upon her). This encounter allows for an exploration of the patient’s deep desires, and her degree of resistance in disavowal or the veneer of conformism. It is this dialectic of desire and resistance which allows a diagnosis to be made in economic terms since, fundamentally, it is desire that builds alienation. The contract is a technical artifice, which provokes a separation situation deeply feared by both the patient and her family, and which reveals the complexity (nature, intensity, ambivalence) of parent-child bonds and the fantasies they have generated. It allows us to study the central issue of separation: procrastination about the weight at the moment of separation and the weight at the moment of leaving the hospital, fetishism of a certain weight, reactivation of separation issues when the patient is discharged from the institution. Adopting the language of the symptom and placing it within the framework of the weight contract, the psychiatrist can then deploy his offer of living treatment within the psychotherapeutic space.