I think starvation mode is completely overblown. Sure, the body is adaptable and if you restrict calories for very long periods of time, your body will probably adapt somewhat. But it's a system that needs energy to work. Too much fuel, and you store what you don't use. Too little and you'll burn fat and muscle. Anorexics take it to great depths - they deplete so much stored energy, that they can lose hair, teeth, life.