DePorter DP, et al. – Here, the clinicians intended to inquire whether sleep deprivation reduces orexin function in ventrolateral preoptic area (VLPO) and to test the hypothesis that sleep deprivation would attenuate the orexin–A–stimulated increase in arousal, physical activity (PA), and energy expenditure (EE). The results illustrated that sleep deprivation may reduce sensitivity to endogenous stimuli that enhance EE due to PA and thus stimulate weight gain.