Why do people needed to sleep?

I do believe that food can supplement body's energy but I'm really confused why people needed to sleep? is it needed to refresh the mind? a food supplement of mind?, the 16hours long that we are in reality keeping busy and doing lotcha stuffs regulating the hemisphere to function normally? and I noticed that some of those who does not sleep as much as 8more hours eat a lot, can I eat a lot and dont sleep?.. is it abnormality if I do so? or I cant think over the limits If I do so? am I a jerk or what? why am I thinking these?