You are enlisted for the army and trying to get in shape. My bets are on the gym. Might sound silly, but I really think you should get in shape there and find yourself losing body fat. I'm not saying you'll lose weight, as you will be gaining muscle, but you will lose fat. I'd put my money on rowers, treadmills and crosstrainers, with a little weight lifting thrown in as well.
Though remember, as you will be gaining weight from muscles, and are not losing weight from fat, your body fat percentage will drop as well!!
Besides the gym you might cut a bit on the potato's and other potato related products.