Support is, at times, hard to give a person living with an eating disorder.
He or she will most likely push you away when you try to help them, and they will isolate themselves as much as they can, as well as abuse things like laxatives, ipecac, and diuretics. They will sneak in exercising and hide food when you give it to them, but don't let this discourage or infuriate you. Remember that the eating disorder that he or she has lived with is like an identity to them. Imagine one day waking up in a totally new place. A new house, job, life, planet, etc., with everything that you once knew so well now gone.