Fat or filler injections to upper body
Unfortunately eating disorders do a great deal of damage to our bodies, especially during developmental years. While filler or fat transfers would be "off label" in this area, it may be of value to you, but it could also cost you a great deal of money, and continual money to maintain it. The additional concern would be where to harvest the fat from in your body. So, I would recommend you make some appointments with several board-certified doctors in your area to discuss potential treatment options for you. Your best solution really may be to just maintain a healthy diet for longer - the body has a way of rebuilding but it does take time.
"This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."