Fig. 3.

An illustration of the concept that insufficient sleep triggers a set of neuroendocrine, metabolic, and behavioral adaptations aimed at increasing food intake and conserving energy. Although this coordinated response may have evolved to offset the metabolic cost of extended wakefulness in natural habitats with limited food availability, it can become highly maladaptive in the context of a modern environment that allows many to overeat while maintaining a sedentary lifestyle without sufficient sleep. SA, Sympathetic activity; RMR, resting metabolic rate under basal conditions; FatOx, fraction of energy derived from fat oxidation.