It depends on where you are. Some places you may have nothing but MREs for a year or one hot meal a day and the rest MREs etc. Other bigger FOBs have full dining facilities. When we went to the field in Korea depending on our field site we could have nothing but MREs for a month. In Iraq I was lucky and our home location was a large FOB so we had pretty reliabe access to a DFAC. Nutrionally though the Army seems to be all CW, at least in my experience.
Edit: I should add that it is possible for some to be primal while deployed. SpecOps posts here and has a journal. He is doing very well with it.