I can speak subjectively from my own experience with 9 years of anorexia nervosa. I am completely 'cured' now, physically and psychologically.
First, I consider all eating disorders to be the same problem, even though bingeing may look very different from starving. It's a way of dealing with feelings that we cannot deal with, by stuffing them, purging them, starving them, running away from them… 'controlling' them. You will not see me use the word 'control' without quotations when I'm talking about EDs, because not even the 'glamourous' AN is control - control is choice, and with EDs there is no choice!! That's how they fuel themselves - by giving an 'illusion of control' (this comes from ABA [anorexics and bulimics anonymous], a program that did not cure me, but I took what I liked and left the rest; many people have overcome their EDs with ABA!).
I hate it all but I still do it
I know what that feels like. It's because you have no control. The ED has control.
For us, our ED was directly related to PTSD/C-PTSD. The AN was not the problem, only the [life-threatening] symptom. All of the fear, guilt, shame, self-loathing, worthlessness, hopelessness, helplessness, lack of control, etc, etc that was the PTSD was translated to food and eating and numbers.
*Trigger warning* We used to react with panic (the littles in particular) over salivating, so couldn't eat carbohydrates, especially sugars. Later we realized that this was directly related to the panic around getting wet during the CSA. We had a phobia of constipation which I could not understand until I heard ninchen say 'I want it out', and it all made sense. etc, etc.
*End trigger* Every single one of us was involved somehow, somehow made sense of the behaviours/beliefs around the ED. (I can elaborate if you'd like). So not one of us could 'save' the rest of us.
We needed to do trauma work, years of trauma work. As well as take medication to stop the obsessiveness (Aiden will tell you that it makes it hard for him to think!). Ninchen could not have done her trauma work without her medication (which reduced physiological hyper-arousal).
It was the hardest thing we've ever done - allowing ourselves to be hospitalized (though we discharged ourselves against their advise as soon as we could swallow without crying) and doing the trauma work. We were at a healthy weight for a few years while our head stayed just as sick with AN - weight is just a potential symptom of the problem of EDs, which for us was a symptom of the problem of trauma. You are not cured until your head is at peace.
Hope something I wrote may help you. Feel free to ask us any questions.