Sleep deprivation increases hunger and slows down metabolism, thereby promoting weight gain. The underlying mechanisms include:
Increasing the level of cortisol, thereby promoting increased appetite, a craving for sugar, and weight gain. An elevated cortisol level also interferes with proper utilization of carbohydrates, leading to an increase in the storage of body fat and insulin resistance, a critical step in the development of obesity and diabetes. Elevating ghrelin and reducing leptin. Ghrelin is an appetite-stimulating hormone released mostly by the stomach. When ghrelin levels are up, people feel hungry. Leptin is a hormone, released by fat cells, that promotes a feeling of satiety.
In population studies, a dose-response relationship between short sleep duration and high body mass index (BMI) has been reported across all age groups. This observation alone indicates that sleeping more may help with weight loss. A very detailed analysis from the Wisconsin Sleep Cohort Study, a large sleep study that has been going on in Wisconsin for more than 15 years, provides even more insight. The participants have been filling out questionnaires about their sleep habits, have kept sleep diaries, and have occasionally spent a night in the laboratory, where researchers studied their sleep in more detail. After sleeping overnight in the laboratory, the participants gave blood samples, which were tested for levels of leptin and ghrelin. What the researchers found is that habitual or acute short sleep duration produces low leptin and high ghrelin levels, a powerful recipe for an increased appetite and for a craving for carbohydrate-rich foods, including cake, candy, ice cream, pasta, and bread.