One of the most important rules when thinking about healthy eating is that, you should mind the food you eat, try eating natural food which has not been processed (examples include different types of twinkies, etc.). Natural food which involves eating meat, vegetables, fruit, rice, etc. is what should be strived towards.
It's also important to understand that you have to balance between eating what is good for you and also what you like to eat :)
You should shelter in place under these circumstances. Your office is a safe enough environment that you would encounter more hazards by leaving rather than sheltering in place.
