I love the "Obito doesn't need to eat or sleep" thing, but thinking about it from the perspective of Hashirama's cells providing regeneration rather than completely altering his internal processes..... THAT'S BETTER
No, just think about it. He technically doesn't need to eat, but that doesn't stop his body from destroying his internal organs to obtain nutrients. They simply regenerate, and this process is ongoing
Same thing with lack of sleep, his brain gets inflamed, recovers, then recovers again, and there's so much cortisol in his blood that his heart hurts constantly(but again, he won't die from it)
Perhaps he understands the reason for the increasing pain, perhaps not. In any case, he's too used to it to try to fix it(and it's also an act of sh, because he sincerely believes he deserves it)
It doesn't reduce his productivity, so he doesn't care, but he can still eat something for company(only if he cooked it himself, he doesn't trust anyone enough(he is probably immune to most poisons, but it's better to be safe than sorry))
