When working on a beat I tend to be focused and treat it as if I am working. Half way though the session I usually stop, take a break let my mind reset and re focus which is the time I fill my belly. After that I go back to producing.
Never while working, but especially if your doing a longer session taking breaks is the best thing you can do with your overall productivity. I find that often times I want to sit down and just pump out an entire 3min in like four hours but even if its just like five minitues to drink some water it gives me to time to reflect and figure out where I want to go with the music. Also if your in a recording session at a studio your time is usually limited to around 2 hours and in bigger sessions (the kind I have never engineered) every might be costing thousands of dollars to pay for all the talent there- so in that case not a good idea to take a break to eat to say the least