Board Thread:Theories and Speculation/@comment-3568954-20170503123318/@comment-4961229-20170510160319

Maybe, but you don't just need calories. You also require nutrients for the body to function properly, repair itself, and stay healthy. So while you could live quite a long time on empty calories, eventually you'll develop severe health problems without the right nutrition. Question becomes whether on not Chakra alone can provide, not only calories, but nutrition as well.

We have an indication of this possibility. Byakugo was capable of regenerating severe injuries from chakra alone. It converted chakra into new bodily tissues through accelerated cell division. Cell division requires building blocks or nutrients from somewhere. Since cells didn't get nutrients from food, it had to either be spontaneously created or cannibalized from the damaged tissues and reformed by chakra.

Kyuubi chakra was capable of healing gaping wounds, as well, so we have corroborating evidence. Kimimaro is another ninja capable of spontaneously generating bodily tissues, not only bone, but also healing the wounds the bones made in the flesh, since he wasn't continuously bleeding. And of course, Orochimaru's Oral Rebirth created hole new bodies, apparently from chakra alone. But that's in a class by itself. Not even sure what he's made of.