They just like it I guess btw have you seen zombies dying of starvation in any movie ? ;) I watched in few of them when they told what I told you, something like "they were living underground for 10 years or more and they haven't eaten anything"  I guess they just like our meat :).

Which movie is that? In "28 days later", at the end of movie, infected people (zombies) die from starvation. But, in many other movies, it isn't clearly said, can they die or not, so I leave possibility that they can't die (In which case humanity is doomed for sure).

I can't clearly remember watched lot of them maybe dawn of dead or even resident evil I'm not sure, still it's holywood  ;), everything is possible.