I don't think there is anything wrong with it, and yes you should get away from your desk for a break. But I agree with others that you should maybe drive a little way away, and then it would be even more of a break!
I once had apart-time job at the local (fairly snooty - well, the membership fees were high) golf club; part of the "role" was to cover lunch for the other two women who worked there (all in one office), and had done for eons.
Come to 1pm, and they fetched a stinky meal from the Restuarant, and proceeded to lock the Oofice door. With me trapped inside!
(South-facing office, blinds closed, old building - and the reek of raw onions, or whatever else they added to their meal. I would leave feeling utterly sick.)
If I didn't go home straight away, I wouldsit on the staff room part of/alongside the Kitchen and Chef would make a jacket potato for me. If the Club Secretary passed by, she would loudly say,"Some people have no homes to go to!" without looking at me. This job lasted from December to February and that was a stretch.
Same happened at a Country Hotel; even though I was allowed to eat/food was prepared by the kitchen, and could do some revision in my down-time (reception), other staff had a major moan and I was then told I couldn't eat or read, in order to keep the bar staff happy.
So much for the "Hositality" industry.