If you are underweighted, the first priority will be to renourish your body, which will involve stopping the behaviors and gaining some weight. The reason (theory) for this is not that they are ignoring root causes, but because you can't successfully do therapy when your brain isn't nourished. So working on healthier eating habits, structure, regular eating, etc will be a first priority. But any good program or therapist will definitely get to the rest of it. You'll be working on distress tolerance skills, body image issues, etc. Ideally, you'll also process trauma if you have a history of it and it's a contributing factor.