Lack of sleep is associated with obesity because it disrupts the endocrine system relating to appetite and hunger. Those sleeping less than 6 hours per night have increased adiposity. However, it is unclear whether the sleep causes the weight gain, or instead is a symptom of another variable that leads to weight gain and obesity. Appetite and satiety are controlled by a complex regulator system that involves the hormones ghrelin and leptin, respectively. Some short-term evidence suggests that sleep deprivation increases plasma ghrelin and decreases plasma leptin levels. This then results in stimulation of appetite, although it is not clear if chronic sleep deprivation maintains this hormonal change. Researchers1 have investigated the effect of sleep deprivation on the ingestion of ad libitum quantities of food. Eleven subjects were allowed 5.5 or 8.5 hours in bed for 14 days while staying in a metabolic unit.
During this time calories consumed from snacks and meals, total energy expenditure and serum leptin and ghrelin concentrations were measured. Although those subjects who received 5.5 hours bedtime ate similar quantities of food at meals compared to those who received 8.5 hours, there was an increase in consumption of snack following sleep deprivation (1087 kcal/d versus 866 kcal/d). The snack foods eaten by the sleep deprives subjects included more carbohydrate content (65% versus 61%). All of these changes were not associated with increased energy expenditure, suggesting that the extra calories in the sleep deprived group might result in weight gain. These changes were not related to changes in the levels of ghrelin or leptin, as serum concentrations of these hormones did not change. These results suggest that sleep deprivation results in carbohydrate snacking perhaps as a reward pathway compensation.
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