I've been through basic too (navy 7 years ago). DOn't worry a bit about gaining weight. I decided when I got there that I was going to diet and eat salads and stuff.....woooah big mistake. I stood up about a week after trying this and passed right out. You WILL lose weight at boot camp....don't worry. I technically didn't lose a pound....but I went down two sizes....had to get new uniforms before I graduated. Trust me....they will get you in shape...that's what it's meant to do. I wish I had an RDC here to yell at me and force me to work out. Sure would help alot!!!