You sounded like a conspiracy theorist just there.
Anyway: The first thing a zombie would die from would not likely be to basically starve to death. A human being could just survive a few days without water!
The fact that zombies eat brains could be true because brains is made from 80% water and other than that it it’s solid matter is mostly fat. I don’t know if it contains any proteins, tho.
Edit: I remember seeing or reading somewhere that the first intestinal a predator would eat is the liver because it is full with proteins.