Sleep deprivation has multiple effects on endocrine and metabolic function. In particular, sleep restriction is accompanied by increased cortisol levels in the afternoon and early evening and a shorter quiescent period compared with extended sleep periods. Those alterations could facilitate central and peripheral disturbances that are associated with glucocorticoid excess, such as memory deficits, and are similar to those observed in aging. Thus, chronic sleep loss could contribute to acceleration of the aging process. Sleep restriction is also associated with an impairment of carbohydrate tolerance, similar to that observed in individuals with clinically significant impaired glucose tolerance. Thus, chronic sleep deprivation may increase the risk for diabetes. Finally, sleep plays an important role in energy balance. Partial sleep deprivation was found to be associated with a decrease in plasma levels of leptin and a concomitant increase in plasma levels of ghrelin; subjective ratings of hunger and appetite also increased (the appetite for protein-rich foods was not significantly affected). Moreover, a remarkable correlation was found between the increase in hunger and the increase in the ghrelin:leptin ratio. Thus, the neuroendocrine regulation of appetite and food intake appears to be influenced by sleep duration, and sleep restriction may favor the development of obesity.