At 5'11" and 130 pounds, it'd be pretty safe to say that you have a pretty fast metabolism. That being said, the key to remember is to balance out if not exceed the amount of caloric intake vs your energy expenditure.
That doesn't mean stuff your face though with any crap you can get your hands on until you can barely walk around. The reason why you CAN stuff your face and still stay the same weight is because your metabolism will cause you to shit everything out of your system, so you don't take as much nutrition from it as normal.
If you plan on doing any intensive workouts, you nonetheless still need to keep your body fueled up. (Not to mention your schooling, just sitting in a classroom learning takes up some amount of energy too) Eat moderately sized meals (where you feel satisfied without getting da itus, but always snack on something intermittently throughout the day.You'll find that you won't have to drop a deuce right after every meal this way.
I do about 2 hours of PT in the morning and 3 hours of MCMAP and Combat Conditioning in the evening on top of my regular duties as a Marine, so in addition to eating my 3 meals, I always chow down on a power bar during breaks. Going on a carb load is great before working out, especially if you feel beat at the end of the school/work day. Avoid the fast food if you can, its real easy to tell who eats Carls Jr. and Mcdonalds all the time on base here.