Here's a tough truth: parents can make or break treatment. We can't tiptoe around this. Treatment can fail for a lot of reasons but most of them are really in our hands.
Dr. O'Toole at Kartini describes it just right, and cites some Australian research which backs it up
What Helps Children
"three factors determine outcome in children with anorexia nervosa:
severity of illness
parental unity with treatment team
parental ability to enforce the meal plan/re-nutrition."
I'd add to this that you need to have a treatment team that believes parents should step up and be in charge of feeding, and works to strengthen #2 & #3 and not work against them. The truth is that the great majority of treatment available to families does neither.