I've lost 90+ pounds in the last 6 months on slimgenics. (its great but dont cheer yet, I have another 90 to go... lol)
basically dont eat anything that comes in a box, bag, or can. (except for prunes and frozen produce) The meat department and produce department are your friends. drink at least 80oz of water a day. No (or VERY little) alcohol, even if it is low calorie it slows you way down for losing weight. Make sure you get enough salt, 'cause eating healthy will drastically diminish what a person typically gets, and you will have NO energy. I use roughly 1/2 teaspoon of mortons lite salt per day. Keep red meat low, I only get 3 servings a week, it makes you hold water. Caffeine is ok but keep it low, herbal tea is great, unlimited. Diet sodas are ok up to 24oz per day, but none with carmel coloring or fruit juice. Diet 7up or Sierra Mist are what I get when I do.
I mostly eat tillapia, shrimp, chicken breast, eggs, very moderate cheese (2oz 3 times a week) 8oz of skim/fat free milk a day, mixed salad greens, cucumbers, tomatos, broccoli, oranges, grapefruit, prunes. protien servings are basically 5oz three times a day, three fruits servings, four veggie servings. For starches I eat the little 50 calorie "sandwich rounds" whole wheat only, and three a day. (adding up to roughly 150 calories)
Just some thoughts thrown out from what I've learned, good luck with the Marines, sounds like a great adventure, one of my biggest regrets is having never joining a service. I was going to join the Navy at one point but my dad talked me out of it. Wish he hadn't.