Through the eyes of a fat chick

How do you help a 15yo that doesn’t want to be helped?
I’m struggling so bad to help him, and I’m desperate.

My 15yo son is 6ft tall, at the end of last year he was a fit, healthy, 75kg guy.
Now he’s 53kg, skin and bone, looks like shit, not eating, exercising excessively and recently be diagnosed as anorexic.

He’s seeing a psychologist and a dietitian, and has great support from them. He has great support at home.

He just refuses to eat.

He’s an accomplished inline hockey player, and would love to give up school to play hockey full time. Which is not being encouraged.

Last night he collapsed while playing inline hockey, and had to be helped from the rink by his teammates and the referee. He hadn’t eaten all day. He drinks water and bloody sports drinks excessively but will not eat.
I’ve pulled him out of his hockey squad, and his next tournament so that he’s only playing one night a week instead of 5.

I’m hoping like hell that last night scared the shit out of him, and it’s given him a wake up call, because I don’t know how to get food into him. I’ve tried so many different things, I’m watching my boy slowly kill himself and I don’t know how to stop it.