One thought on anorexia from an untrained but curious layman: 
I read an article many years ago when anorexia first hit the public eye. 

This account told of a young woman who became anorexic after she got her estrogen. 
Before puberty, she and her father were very close, both emotionally and physically. They were buddies. 

When she started to get her figure, he began to physically withdraw from her. 
This frustrated the girl; she felt neglected and unloved. She felt her new body pushed her daddy away. 
The girl began to hate her own body. 

I suspect her anorexia was her way to get her girl-body back, so she could be her daddy’s little buddy again. 

The majority of anorexia cases are females and onset during puberty. 
I suspect many anorectics simply don’t want the bodies they are being given. 
Not every little girl wants to have a woman's body, and everything that goes with it. 

DNA forces us to become different people that we used to be as children. Not everyone welcomes the change. 

(This is no justifuication for a trans-lifestyle.