Some recent significant studies show that sleep plays an important role in our health, particularly in regard to the hormones that are released when we get sufficient, uninterrupted, quality sleep.
When healthy, young people were deprived of sleep, they experienced early signs of aging, glucose intolerance and insulin resistance, which may be markers for the development of cardiovascular disease and diabetes.
A study of adult men showed that, when sleep deprived, they secrete less growth hormone, which can "accelerate the paunch process" and lead to middle-age spread.
Some studies have even indicated a link with weight gain and obesity. The hormone, leptin, is secreted during sleep and makes us feel full. When we do not get enough sleep, leptin levels drop and we crave carbohydrates.
Many researchers believe that our immune system is strengthened during sleep, which helps you to repair tissue and fight infection. Perhaps, this is why sleepiness accompanies illness.
-National Sleep Foundation