helomaa - Does your school have a grocery store where you can spend your student dining dollars? My school had that - we could purchase Lean Cuisines, fruit, milk, etc. instead of eating the hot food.
I know it's tough in college. You're constantly surrounded by not-so-healthy choices. Always keep healthy choices in your room so you won't be tempted to call in pizza when you're studying at 1:00am.
That's the best advice I have. Good luck!