Zombie Science: What do Zombies eat?

Do Zombies Eat Brains?

The zombies in my books and stories don't eat brains.  George Romero's zombies don't eat brains.  Zombies on The Walking Dead don't eat brains.  In fact, according to this Gizmodo article on the topic, the "zombies eat brains" trope didn't appear until John Russo's "Return of the Living Dead" film and was popularized by an episode of The Simpsons.

Zombie photo by KEYWEST.LIFE / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

What Do Zombies Eat?

So what do they eat?  I believe they eat small chunks of and the entrails of people that they kill.  They also feed on animals.  As seen on The Walking Dead, they have eaten deer, horses, and a tiger.  I don't believe that they feed on anything for long.   Otherwise, zombies wouldn't leave enough dead body to be animated into a zombie and the contagion wouldn't spread. Zombies may not eat much.  They most likely don't have fully functioning digestive systems.  However, their brains must contain some drive that forces them to press on and find new humans to bite, maul, and eviscerate.