"I have to eat food."
Translation:मुझे खाना खाना है।
Why can't it be मुझे खाने खाना है? Since food is the object so it needs to take oblique case.
The verb खाना is a transitive verb which means it can take direct objects. In this case, the noun खाना is a direct object of the verb. So, there is no postposition required between them and no need of the oblique case.