Lack of sleep and Obesity

Over the past several decades, the prevalence of obesity has grown to epidemic proportions. Concurrent with this rise in weight has been a similar epidemic of sleep deprivation. According to annual surveys done by the National Sleep Foundation, by 1998 only 35% of American adults were getting 8 hours of sleep per night, and that number fell to 26% by 2005.
A review of literature performed by the National Institutes of Health suggests that short sleep duration is strongly and consistently associated with concurrent and future obesity in children and adults. A number of mechanisms have been proposed including the idea that chronic sleep deprivation can cause feelings of fatigue which may lead to reduced physical activity. Perhaps more importantly, however, sleep deprivation may have metabolic and endocrine effects that increase caloric intake by affecting leptin, ghrelin, cortisol and insulin secretion.
Leptin plays a key role in regulating energy intake and energy expenditure by inhibiting appetite and increasing satiety. The absence of leptin leads to uncontrolled food intake and resulting obesity. Conversely, ghrelin is a hormone that stimulates hunger. Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of leptin.
Laboratory studies have shown that sleep deprivation may increase the risk of weight gain and obesity by upregulating appetite via a decrease in leptin, and an increase in ghrelin.
It is well known that glucocorticoid use increases food intake, and alterations in cortisol levels associated with sleep deprivation can lead to an increase in food cravings, particularly sugar and salt. Additionally, studies have shown that sleep deprivation leads to reduced insulin sensitivity, which can result in a prediabetic state and an increased risk for weight gain and obesity.