Having no food can starve a person to death!
Zhou Tian should feel fortunate now that he used to be a human. It was a good thing he had been human, so this feeling was not unfamiliar to him. Otherwise, if Zhou Tian had been born a monster, with no knowledge of hunger and food, he might not know to seek food when his stomach was empty. And if he didn't look for food at the first sign of hunger, even if he didn't starve to death, by the time he realized he should find food, he probably would have already been too weak from hunger!
Now, although Zhou Tian didn't understand why there was still a feeling of emptiness in his stomach even though he had become a monster, since he felt hungry, he clearly knew what to do next.
Since he was hungry, he might as well think of a way to get some food.