Running a accelerator, one thing we've discovered with feeding our startups is that bringing in food has another beneficial side effect: stress reduction.
We try to cater at least three meals a week for our folks. Because we've seen the benefits: 1) Makes sure that people are actually stopping to eat. 2) Lowers the burn rate for the companies. 3) Lowers stressing about "Where are we going to eat?" 4) And perhaps the most beneficial: It ensures that we're forcing some actual nutrients into their diets.
Of course the other fringe benefit is the peer mentoring and socializing, where people actually stop banging on keyboards and take a moment to talk to one another.