I met a guy at the gym in his 40's and he was the leanest dude I ever saw, he wasn't big, but just reasonable build, but really fucking lean. He told me he doesn't eat anymore (digestion solid food takes too much energy he said) and he just makes all type of weird juices out of vegetables and fruits and the like. He was a strange hippy type who rode a motorbike, lived in the hills and managed some type of weird holistic healing centre.