Apple, I think that this is something that is so dependent on the doctor. the individual and their unique situation that it's impossible to answer your question.
I have not heard of eating disorders being something that keeps a person from getting HRT but I suppose it's quite possible.
I think testosterone would make you hungry and want to gain weight anyway, it certainly did that for me when I was a teen.
I wish I could be more helpful.
hugs & smiles
helen