Why is my brother wanting to divorce his wife over this?

My little brother and his high school sweetheart are 24 and been married 6 years. Well he has battled bulimarexia since he was 13 well his wife i thought kind of healed him of it because once they fell in love and and dated all through high school he got much much better. Well now its resurfacing and we are all unsure why he isn't depressed they are still madly in love and expecting there first child a boy that is due on new years eve. Well he has started to starve himself and purge when he does eat and his wife just asked him to get some help or to eat or talk to her and everything. And my baby brother flipped chit on her and left an dis now at a hotel and is wanting a divorce i do not understand wtf is going on with him. What should we do? How can i get through to him? Advice?