It's all about your level of commitment to fitness.
If you're worried about balancing a social life and fitting in work outs, why not just make going to the gym a social thing? Go with a couple of friends - you'll need somebody to be your spotter anyways if you're doing any lifting, and it's always nice to have a buddy to do your cardio work outs with!
And no, univeristy does not automatically mean study all day, every day. it's about balance. I personally cannot sit down and study for 6 hours straight if I haven't gotten in a good amount of exercise.
Your brain also functions better when you have had exercise, which means you can get the same effect as studying for a long time by studying for smaller blocks of time, but being more efficient in those times. Same goes for sleep; no sleep means you won't be able to focus and then studying just becomes a waste of time.
Figure out a routine that works for you - going to the gym in the morning, between classes or at the end of the day - and make sure you balance your life out - and you will be fine.
Oh, and avoiding the pizza can't hurt either!