Old motto: Eat when you can, sleep when you can, urinate/BM when you can.
If this is seriously a problem, then you should carry around some food in your lab coat pocket, especially if you will be working/studying at a med centre without 24/7 food service. Crackers and cheese, cheese sticks, small boxes of raisins, etc. will all fit into your coat pocket and can be readily and rapidly eaten if you find yourself dropping. This is particularly important during surgical rotations when the hours, the stress and the standing can do in the most hardy of students.
You may find it hard to believe, but it is pretty rare IMHO to work extended hours without ANY time given to eat - I dunno about other specialties much, but there is a great deal of waiting around time in surgery, and ample time to sneak a snack if one is hungry. Don't believe the hype that its all 48 hour shifts with no sleep, no eats, no...
Hope this helps.
PS: because this is a topic for the Rotations and Residencies Forum, I'll move it for ya.