Board Thread:Theories and Speculation/@comment-28323245-20170530200422/@comment-1920550-20170531225641

Hashirama most certainly needed to eat, sleep and drink, Wood Release or not. While his life force (physical capabilities, durability, longevity, healing factor) we're second to none, he was still a living, breathing, bleeding human being.

The White Zetsus, while created from his DNA were artificial creatures (living plants so to speak), who had a series of human necessities (nutrientional intake and restoration rituals) either significantly altered or completely removed. Since a large portion of Obito's body was remade with this material, that was why he gained these benefits.

This also serves as a simple explanation as to why Obito has so much chakra, vitality and suffers minimal backlash from extended MS use. While most other characters we're either spliced with Hashirama's DNA at childhood (Yamato) or had their bodies grafted with it (Danzo and Madara), Obito had a significant portion of his body that was completely rebuild by a material based on the First's DNA. Serves to reason that as such his vitality and healing is much stronger when compared to pretty much all other people who were spliced with his DNA.

As for dojutsu, all of them caused visual and body strain and chakra drainage to varying degrees. The only exceptions to this were from those who we're the jinnchirki of the Ten-Tails or of the Otsutsuki bloodline (who let's face it, amounted to physical gods).