The first morning I met Kevin Crain, a Managing Director at Bank of America/Merrill Lynch, he was feeling tired, as he did most days.We were at a conference Kevin was hosting for the institutional retirement team and a group of their corporate clients. He'd invited me to the event to speak about managing personal energy.Before my talk, we got to chatting and Kevin mentioned that he'd gotten less than six hours of sleep the night before, and that he didn't often get much more.

Let's cut to the chase. Say you decide to go on a fast, and so you effectively starve yourself for a week. At the end of seven days, how would you be feeling? You'd probably be hungry, perhaps a little weak, and almost certainly somewhat thinner. But basically you'd be fine. Now let's say you deprive yourself of sleep for a week. Not so good. After several days, you'd be almost completely unable to function. That's why Amnesty International lists sleep deprivation as a form of torture.