We know sleep deprivation comes at a cost, and now we know precisely how much, at least in caloric terms. After studying subjects who lived in a sealed room for three days, University of Colorado researchers calculated that the body burns an extra 161 calories to fuel an all-nighter. As Science News points out, it's the equivalent of a warm glass of milk. For those thinking they can burn off extra pounds by forgoing sleep, forget it. The body tries to make up for the deficit it the next day by saving extra energy.