Unless he is making chlorophyll in his cells, he's going to be one blind, dead hippy unless he eats something.
There is also the small matter of cellular components to account for. Unless 'sun gazing' converts photons into actual molecules....
It hurts for me to write that.
Don't worry, he's eating. I saw a special on one of these guys once, and they're like Cindy Sheehan in that they don't count their various sources of actual nourishment as "food."