Even if they actually had anorexia at some point, how is letting them overeat helping them?  If an alcoholic has to completely abstain from alcohol in order to fight their addiction, they still have trouble with it and haven't actually dealt with the real issue.  And that's still a shit example because it would at least be the obvious best of both extremes; I honestly couldn't think of an accurate analogy for an 'anorexic' overeating.  Jumping from one extreme to another isn't good.