I have carried lunch. Sometimes just ziplock bags stuffed into a plastic grocery bag. I've carried leftovers in 'tupperware (or facsimile)'.

I've gone to buying groceries and just keeping it in the office kitchen.
I have a fridge and a microwave, so sandwich fixin's and canned soups and such are easy.
This is only shared with like 3 others on my floor.. so it works out OK.