Most of the time it's leftovers from the night before. I tend to make dinners a bit larger on purpose so I can have a cheap lunch the next day. Sometimes it's a sandwich/soup from the cafeteria/coffee bar (we have a pretty good and healthy food service at work so I don't feel guilty about it). In summer I'll maybe bike out to have lunch with people every now and then, but I purposefully have a shorter lunch break so I can leave work earlier than others. No fast food from chain restaurants. That's a personal "food rule" for me.