I cant comment on the armed forces aspect, but I can give you some advice on the nutrition/getting in shape.
When I was younger I was, and helped train elite atheletes. I fell out of shape at 30 due to being able to afford to eat
and having shoulder/knee surgery.
I have always trained, and worked out, and even when I was over weight, I still _thought_ i was in shape. (Everyone always does, until you see the pictures).
I changed my lifestyle and eating habits by reading a book called.
The ABS: Eat right every time guide.
Its part of the ABS diet /exercise program. Its cheap, you can get it on amazon for $7 or less. It is the best book, on nutrition I have ever read. Its a no nonsense, cut to the chase, answer your questions type of book. Its made for men wanting to get fit and strong, and be healthier.
It has a whole section just on 'if you have to eat fast food eat this, not this'. broken down by establishment.
I used it after my surgery (I picked it up on a plane trip) it was about 90 small pages. I read it before I got off the plane, and I have recommended it to at least 10 personal friends, and _most_ of them have made dramatic improvements in the bodies.
Its not going to diet you rail thin though. It explains how to feed your body properly, and provide it with the proper nutrients to sustain muscle but lose fat.
I highly recommend it, and all the books in this series. This one though, is far and beyond the best. It has all the usefull information the others have (diet wise) but a lot less filler content.
Good luck and stay safe.
Mason