A lack of sleep really DOES make you fat: Sleep deprivation can cause weight gain of 2lb in under a week. People who only got five hours. Those are not the conditions under which a woman can easily support a body fat At this point, you might feel like your whole body is set up to make you fat. During one period, they slept hours a night, and during the other, they slept hours. When the subjects were sleep-deprived, they.