When medical staff see someone resolutely starving themselves in a state psychiatric institution, drinking liters of water before their daily weigh-ins to nudge

When medical staff see someone resolutely starving themselves in a state psychiatric institution, drinking liters of water before their daily weigh-ins to nudge the number up, and hiding their full Ensure cans from nurses to avoid the calories, it is hard to chalk it all up to any normal and relatable definitions of the words habit or willpower, especially given that the behavior overcomes the drive for energy consumption, one of the strongest and most primitive drives in all organisms, and one which seems abolished in a deranged fashion. Even if habituation plays a major role in the development of the disease, it is hard to seriously consider the proposed solutions like "switch to eating with the left hand, as a reminder to think about eating different foods" as promising therapies in cases of recalcitrant anorexia. Which is not to say it won't be tried; I imagine side effects are minimal...