Moderate levels of fitness can also be accomplished by choosing to exercise when and where you can. Options include taking the stairs instead of the elevator, walking or biking to and from classes or to and from work, walking a dog, cleaning your room or apartment, shoveling snow for 15 minutes, and doing household chores such as laundry or washing windows. When you're studying, be sure and get up and move around every hour. This will get the blood flowing and help to relieve stress. Some light stretching would be good also.
Recreational activities count too.
Take a close look at your current schedule. Plan ahead when registering for your next semester classes. Or better yet, take a P.E. course. If you are a full-time student anyway it won't make much of a difference in your tuition bill. The key to a healthy, active lifestyle is to recognize the barriers that exist that keep you from being active and to allow yourself to be creative about developing strategies that will break down these barriers.