Typically 4 days/week. I work out in my company's exercise room (we have treadmills, ellipticals, bicycles, and a weight machine), and by the time I get done exercising (typically after a half hour), I don't have time to go out. So I nuke something up in one of the microwaves that's in the pantry next to the lunchroom, eat it in my office (surfing the net while doing so), and get back to work. Fridays I typically go for a short walk outside, and grab something at the drive through of one of the fast food places near where I work. Ditto, for grabbing a quick bite at a fast food joint's drive through, if I need to run errands at lunchtime, during the rest of the work week.