I lose weight at uni. Mainly because I'm too lazy to go to Sainsbury's, but have to walk around for other stuff. Sometimes I go for ages without feeling that hungry, and thus have even less motivation to go to Sainsbury's (yes, I am fully aware that this is not healthy before someone says it!). I also have really bad sleeping habits as I seem to end up working at night - in bad weeks I will have 2 all-nighters for essays! (again, I know this is bad for me, and I don't do it on purpose!). You should be able to avoid that one by being more organised, or actually just by not taking an entire day and night to write one essay...I've got very slow recently and actually used not to need all-nighters.
Generally, it is up to you what you eat/how much sleep you get so if you take care you should be able to keep healthy. My main problem with it is that I don't put effort into thinking about staying healthy, as I suspect is the case with many students!