system
Given the following post, respond as if you're commenting on Reddit:
human
[iZombie TV Show] Why do zombies eat daily doses of brain?

> “You know what you're looking at?"
> "A brain?"
> "You're looking at 20,000 dollars, one of these can last a zombie a full month"

In the show it’s stated that a single brain can last a zombie a month, but when separated from their food source for over 24 hours extreme uncontrollable hunger sets it. This is presumably because the zombies ration their brains for daily consumption. Either this is by choice or because a zombie grows hungry regardless of a full stomach. (I just started Season 4, so if there’s an explanation forgive me)

Assuming it’s the former, this diet doesn’t make much practical sense. It may work for Liv who has to frequently switch between murder victims. But I don’t see how it benefits the two other zombies we see in-prisoned nor the rest of zombie society who have enough problems feeding themselves as is. For example: >!When Filmore Graves is rationing out brains, in a food shortage and while fighting humans, would it not be far easier and safer to supply and eat them once a month rather deliver a supply and put the tubes in storage to be eaten across the month?!< additionally this method would mean fighting visions and personality disorder in shorter and possibly stronger bursts. Also Zombies don’t even like the taste. A tasteful diet for them would be snacking on peppers if you really got the munchies.

Assuming it’s the latter, this answers the title, but raises serious questions on the sustainability of zombies. For one, overeating should be a much bigger problem. I mean human hunger is controllable to the point we can starve ourselves to death and we still have an obesity problem. Imagine what a Zombie’s daily hunger would do. Every time a delivery was late and the hungry zombie ate a little too much, they would need to eat even more brains that month. Eventually these insistences add up and suddenly Blaine would need to kill twice as many people. Those same zombies would also have to be really good at packing brains with them on every out of state trip, or out for the day, or visiting anyone. Or they all just got away with murder easily. And this without even considering zombie island. >!It’s hard enough to get monthly brains for a city half full of zombies. And remember how many starving kids there were? What stopped those guys from going rabbits day one?!< The level of error involved with feeding zombies, both biological and practical, makes such a city impossible to feed. One of the hundreds of zombies in hiding should have went rabbit after after a year or so. What could have possibly prevented the apocalypse?
gpt
It seems that the infection makes their bodies stop producing certain chemicals necessary for higher brain function, and they have to acquire those chemicals by eating brains. Starve a zombie of brain matter, and they become stupid and hungry.

You are correct, Graves' plan is only a short-term solution, not manageable in the long run, and it could turn into a "zombie apocalypse" scenario under the right circumstances. The primary reason it hasn't is that zombies are compelled to stop after one kill and eat the brains of their victims, which prevents the victims from rising as new zombies. It doesn't spread unless their victim survives the attack.

This means outbreaks are manageable, they progress reasonably slowly, more like the pattern of a serial killer than a contagious outbreak.