I'm no longer a college student, but I thought I'd share my experience. I packed on a nice freshman 20, then stayed on campus for a language program over the summer and was able to put it off, and a rough breakup with my freshman year boyfriend actually helped me lose some more sophomore fall till I was at my lowest in like 3 or 4 years. But, a new boyfriend led to packing on another 20, which I then put off over the summer (again I was on campus living in a dorm and eating in an all you can eat dining hall). I went abroad to Spain junior year and packed the pounds back on again, but that summer I fractured my foot and kept gaining instead of putting it off, leading me to graduate my senior year the heaviest I'd ever been, a full 40lbs up from my freshman year weight.
I think I was able to put off weight in the summers bc I took up running outside, and also the food in the dining halls included a lot more fresh fruits and veggies so a typical meal for me would be like turkey, veggies, and hummus in a pita as opposed to the regular academic year when i'd eat maybe a hamburger, a bowl of creamy soup, and a piece of cake. I also went to school in the Northeast (and am originally from MD as well), so Bluebird you might have a similar experience being less active in winter and having healthier foods be less readily available. I think if I were more conscious of what my habits were doing to me at the time, I might have been more proactive about going to the gym.
A word about the gym--this may not be your situation, but the gym at my college was filled with athletes and was always really crowded, and I found that really intimidating. It was also all the way across campus and so except for the few times I went on fitness kicks, I rarely ended up going, but I felt like bc it was free it should really be my only option. Now I still live in my college town and could still use the gym for free, but realize that paying for a gym membership to a different fitness center has made a world of difference for me. First of all, they offer classes which the college gym did not, so that forces me to be there for class and as a bonus I've found I really love spinning and love going and love the people I've met in the class. Second of all, the atmosphere is just sooo much better...in the winter I go all the time bc there is parking and I can drive (unlike my college gym) and they have a sauna which is something I can really look forward too. I find the whole experience really relaxing. Third, I'm paying for my membership so that's an extra motivator--the more times I go, the less the cost is per visit. and I justify it a little bit bc now that I have to pay for my hot water, I save money on my electricity bills by showering at the gym
Some or none of these circumstances may apply to you, and you may not be in a position to buy a gym membership, but I didn't even think about a gym membership at college because I had the free gym, and in the end, it could have been really good for me.
I can't offer much sage advice about the dining halls...my college had fantastic food and I ate a lot of it!