I read a book by Linda Goodman when I was about 13 yrs old. Star Signs / Sun Signs? Something like that.
Talked about various levels of eating and that you could wean yourself off meat, then off veggies to eat only fruit, then off fruit so that you only need the direct sun.
I entertained the notion on and off for a bit but as I have easily burned skin, I decided living off the sun wasn’t for me.