[Daho0n]

>The body can adapt quite nicely to many foodstuffs

In a perfect world yes, but we live in a world where (at least in the West) pretty much everyone is addicted to sugar. A healthy body could switch between burning fat and burning glucose but I have yet to meet anyone who can do this without having been eating keto for a while. It's harder but possible as a vegan and I would recommend it to anyone. Just once and the body is better at switching back and forth.