There are various reasons why zinc supplementation may be useful. One is that it is involved in appetite control and taste - so both would go if you were low in zinc. Studies have shown more than half of anorexics have zinc deficiencies. Since zinc is needed by the body to digest and use protein, an anorexic would need extra zinc once they started to eat and gain weight. Studies have also shown that taking zinc supplements help improve mood and reduce anxiety - which can help anorexics deal with the psychological aspects of their condition. So I recommend supplementing 30mg of zinc daily in addition to any other help they are getting.