Cadiuro:
''The Zombie craves fresh human flesh. Some have suggested that eating the living reminds them of the life they once had. Still others say that the Zombie is reduced to its most basic desire by its reanimation: the need to feed. The creature instinctively and physically driven by the desire to feed.
The Zombie’s instincts are rather limited. However, their one driving instinct is the need to feed. The preferred food is warm human flesh, preferably taken from a still-living victim. As to exactly why the Zombie feels this unholy hunger, no actual answer has ever been given. However, theories abound, and the most accepted theory is instinct. Hunger is one of mankind’s oldest drives, an instinct that instantly takes hold upon birth. As mentioned earlier, this creature is little more than walking, motorized instinct. So to some extent, this theory makes some sense. The Zombie’s craving for living flesh isn’t an actual physical need, but rather is psychological in nature. The creature will continue to attack and kill, even if it has no stomach. A decapitated head will still attempt to bite, even though it has no body. Moreover, the Zombie will refuse other kinds of meat when it is offered. So, why does the Zombie feel the need to kill and feed? Obviously not to satisfy any type of hunger. The creature’s brain is slowly decaying, and when most of the brain has rotted away, only the most primitive parts remain. With this comes the most primeval of all urges, inherited from the reptiles and amphibians: hunger, the need to feed. As a consequence, the Zombie doesn’t actually need human flesh. It has no metabolism to speak of, and therefore the ingested flesh is never converted into energy. The creature just continues to eat until its stomach literally bursts. What’s left of the brain makes the Zombie think it needs to feed, and therefore it attacks humans to satisfy this craving. As a result, this fills the creature with a savage, unceasing hunger for life."