Hi sorry you and your friend are going through this. I agree with everyone that he should try seeing a doctor at some point but i wanted to add, are you sure "his problems" that you mentioned are unique to him/his condition (or whatever)? He's at the age where there's lots of changes going on witg the body suddenly and that can be freaky/scary, but entirely normal.

I'm not trying to downplay his troubles though, I'm just thinking it might be unnecessarily stressful for either of you to think something is "wrong" with him when that might not actually be the case, yknow? But I'll let you be the judge bc idek what problems he's having

And also, I googled it and 90 pounds is pretty normal at that age, so if that's his actual weight there's probably nothing wrong there. Some people just "wear" their weight differently sometimes