The biggest problem I had as a student was a tendency to wait too long between meals. It's the nature of the work: sometimes you really do need to be in place for six or eight hours without a proper meal break, and 15 minutes isn't enough time to even run to McDonalds, let alone assemble a full meal, so by the end of it I'd get in the door and stuff my face with whatever was convenient.
What worked for me was snacking throughout the day. These days I'll pack a sandwich of some description, a can of microwaveable instant soup, a ziploc bag of dry cereal, a banana, a pre-cooked salmon fillet, etc. and I'll just eat as I get opportunities to do so. This means sneaking off to the lunchroom (No food in the house or on deck! EVER!), but I only need two minutes to snarf down a BLT and it gets me through the day much better: when I get home, I'm not absolutely starving, so I can take the time to prepare something worth eating.
I think it's likely I'm eating more food than I ever have before, but I've lost weight and I'm spending less. (I can get everything in my lunchbox--which will last me through a full day and replace my lunch--for less than a fast food combo meal.) Funny how that works.
If I was on tour I don't know what I'd do, heh.
I'm trying to replace soda with seltzer, but most of the soda I drink is in restaurants anyway, and it's not like Burger King will bring out a spritzer bottle for you.