It seems to me that the problem people have again and again with all such issues, such as weight loss, smoking etc.. is that the more they try the more they fixate on the issue and inevitably are overwhelmed. I wonder if there is not an intervening step required to make it easy. Hard things tend to not get done and easy things do.
I have an idea which might help. It is simple and free. It seems too easy but it works for me.
The idea is a visualization exercise. You imagine a Switch. I visualize a big electric Switch. You place the Switch in your mind. It is just in there somewhere. You use the Switch when you want to make a serious decision like achieving a normal body weight and stopping abusing food. Once you have thrown the Switch just eat normally get nutritional advice if necessary - and if you have any temptation to backslide then visualize the Switch not the the issue. This avoids fixating on the issue. Instead focus on the issue of gaining self control. This puts your focus where it should be and not where it will inevitably result in losing self control.
I think this is the mechanism people have who appear to have discipline.
There is a discipline involved but it is clever discipline. Do not beat yourself up or you will loose. Balance yourself and it is easy.
Hope it helps. :)