Bottom Line Up Front (BLUF):
Medical can supersede the weight chapter. Part of the weight chapter is medical counseling. Consider using this opportunity to speak with a doctor about the med board desire. The unit is most likely trying to get rid of you quickly as a chapter is quicker then a med board.
A doctor can put you in the med-board process simply by giving you a P3 profile. If you have bulimia I am sure you are seeing a doctor at the hospital or clinic. Going through the unit PA will not help as that person will usually follow what the Commander wants.
You will still qualify for VA benefits and can apply for VA disability even if they chapter you for weight. Weight is an automatic honorable discharge.
Office of Soldier’s Counsel
Recommend you consider speaking with an attorney at the Office of Soldiers Counsel on base. They are the ones that represent Soldiers going through the med board process and speak to them about seeking treatment as well.