Why Zombies eat Brains

Much of my research focused on physical and psychological needs for zombies to eat brains, as well as habitat needs.

One study found that the undead have a significant reduction in the pineal gland. Perhaps Zombies are compensating for a lack of this significant area of the brain, and by eating brains they feel they will make up for the lack of theirs.
Brains are also very high in protein/nutrients.

Recent studies have shown that glial cells, which make up the bulk of a brain, have the ability to act as stem cells, at least as far as being able to replicate other brain cells. Zombies are probably going after the glial cells to help restore some of their brain function.

Brains are also rich in cholesterol, which is essential for maintaining cell membrane pliability, which is a particular problem at the low body temperatures typical of zombies in non-tropical climates.

Psychologically, the act of eating brains can ease the pain of being dead (see movie "From Beyond")This would actually make more sense, when one considers some studies which note that zombies probably don't eat for nourishment, and perhaps the act of brain-eating represents an unholy, instinctive attempt on the undead's part to regain their lost minds.

Also we need to consider that by being dead, many zombies are missing teeth, and prefer eating something that's easy on the gums.

One last idea is that zombies eat brains as a matter of managing their habitat. As is well-known, a zombie's bite will infect a normal human and turn him or her into another zombie within a matter of minutes or hours. This, of course, assumes that the attacking zombie or its pack do not completely consume the victim. Now, you figure that a solo zombie or even one or two attacking in conjunction cannot eat all of the meat parts of a given victim in one sitting. This means that if a zombie just eats an arm, pretty soon it will be joined by a one-armed zombie that is also now on the hunt. Therefore it must now compete with the nub zombies in the pursuit of tasty human flesh. Eating the brain is both satisfying and prevents the rise of new zombies, so the zombie population does not increase to unsustainable levels.