How to Ensure a Teen's Recovery From an Eating Disorder Lasts?

How do you know when a teen or a young adult needs professional help? And then how to ensure when they do get that help that the recovery will last? Recovery is, can be a long-term thing. It could be two to three years but when you see them back engaging in their life, that's when you start to know that they're getting better and they're being consistent with their nutritional needs.