A zombie walks into a tiki bar. "Hey," says the bartender, "did you know we have a drink named after you?" The zombie looks surprised. "You have a drink called Marvin?" he asks.
That has nothing to do with what zombies eat. It's just to lighten the mood a little, because this is a pretty grim story.
It's a grim story because, according to the experts — chief among them Max Brooks, author of The Zombie Survival Guide: Complete Protection from the Living Dead and the novel on which the recent Brad Pitt vehicle World War Z was based — what zombies eat is you. Or those like you.
But is this really true? Brooks obviously knows a lot about the dietary preferences of the undead. He tells us that zombies are definitely not gourmets, to begin with. Some reports maintain that what these creatures from beyond the grave really like is brains (and not au beurre noir) — a refinement, if that's the right word, that may have been first suggested by the 1985 zombie flick Return of the Living Dead. (In a more recent foray into zombieland, Warm Bodies, zombies eat brains so they can take on the memories contained therein.) Brooks doesn't buy the brain thing, though, maintaining that these animated corpses just like human meat of any kind. They do have the ability to distinguish our flesh from that of animals, and they express a preference for freshly killed meat (if you've been dead for 18 hours, don't worry; the zombies will shun you faster than a Gwyneth Paltrow shuns a Baconator), but they have yet to betray a preference for, say, Chinese or Mexican over Lithuanian or Tahitian — or vice versa — when it comes to reaching for a snack.
Brooks also tells us that zombies are sort of piggy: They eat night and day — but not, apparently, because they're always hungry. Food isn't fuel for zombies. They don't need it to survive, and in fact can't even digest it. It just sits there in their zombie tummies and ferments, sometimes to the point that their guts explode. Which doesn't seem to bother them much.
If zombies don't need food, then why do they keep eating folks? Some "zombieologists" posit that it may be to stave off the pain and suffering induced by their condition. Brooks seems to think it's just a base instinct — about all they have left — and as a way of zombifying others. I think it's maybe just because they're mean.