I work in a college - so not exactly the same.
1 - ask your instructors if they mind if you snack in class. I think as long as the food isn't overly noisly (crinkly bags etc) they probably won't have a problem with it. You could also go to a doctor and have them write a note for you saying that you need food throughout the day (not exactly a lie, but most Dr's will understand).
2 - Do you live on campus? If not, walking to and from (or at least part way) daily can help you get in some exercise (that is what I was doing for quite a while... 4 km total per day until it got too darned cold).
- Too cold to walk, invest in some workout videos
3 - Is there a gym? Being a student, can you get discounts? Try to get in at least 30 minutes a few times a week (better than none at all).
4 - Take breaks in between studying. Sitting for long periods of time will tire you out while studying. Take a 20 minute break, wear an MP3 and go for a quick walk. It will help clear your mind, and you'll reatain more during study.
5- Cutting back on caffine can help as well - replace it with fresh fruits. There was a study saying an apple gives you as much energy as 1 cup of coffee.
6 - stay away from Campus foods if possible, even though the food may look healthy - they try to save money on getting cheaper foods (e.g. Chicken wraps are usually made with the processed chicken, lots of fat, not much protein - you can buy all white meat precooked chicken strips, veggies and tortillas for almost the same price as 1 single meal on campus... this can last you up to a week. You can also freeze the tortillas and chicken and take out what you need when you need).