It is hard, at first, for parents to understand that a loved one is ill when they are still functioning so well at school, still running track, still so motivated to achieve and so articulate and focused. Logically, if malnutrition was damaging the person they would be weak and fuzzy-headed, right?
Lesson 3.5 in Eating Disorder Parenting: The ability to focus and be motivated can be (temporarily) improved by semi-starvation. The "need" to stay in sports and achieve in school can be a symptom of being mentally UNwell. By the time malnutrition affects academics and even sports, your loved one may be permanently brain damaged or worse. Homework: Put recovery before everything else. Refuse to enable any activities that interfere with recovery.