I think you're missing the intended meaning of the request, ergo what witch said:
But if they've just been fed, they wouldn't want to eat again immediately, surely?
Sure, it does kick in as a hunger respose, but rather flakily & unreliably. It'll kick in as a hunger respose usually after the zombie has eaten. It definitely kicks in as a social interaction. (ie: the "OMFG, she's hot, I must lunch on her lobes" response) But generally, if a zombie is in the red hunger-wise, it will die of starvation before lunching on anyone.
So.... is this working as intended then, or are zombies supposed to be fixing themselves a snack of their neighbours when they're hungry?