Starving for 18 days?

i am not going to do this so dont tell me not to, im not an idiot. i was just curious, if someone was to eat nothing for 18 days. what would happen to the body at the end of those days? besides being tired and weary. would a person lose weight? how much, if they would? what would it depend on? does anyone have any clue? also, i knoiw that as soon as the person would eat again, theyd lose weight.