I've done the best when I've just worked on changing one habit. That way I don't get overwhelmed with it all. Right now it's all nightshade foods, guess I'm allergic to them (i really, really really hate rashes!). So I don't really concentrate on any other habit until I get the current on under some control.
My mom is underweight too, she just can't keep weight on. Perhaps some part of the binge is the body needing more nutrients. That's a theory I;ve heard in the past about cravings. My hubby and I had Mom starting eating the sweetest "good for you" sandwich and it's helped. It's raw unfiltered honey (it's strained of junk though) and cinnimon mixed together and spread on bread for a sandwich, like PB and J. The reciepe is 1 teaspoon cinnimon and 3 teaspoons honey mixed together (slowly, cinnimon really fly's) and spread on bread (toasted or untoasted). The raw honey is really good for the body. Just a thought. :)