Sleep is one of the body’s most active states. When the body is in non-REM deep sleep, it signals your pituitary gland to secrete growth hormones to stimulate tissue growth and muscle repair. The brain moves short-term muscle memory into long-term muscle memory during sleep as well. Your immune system is also strengthened.
Research has proven that people who sleep fewer than six hours a night are more likely to catch colds. Research has also found that those who didn’t get adequate sleep showed decreased levels of leptin (which manages feelings of satiety) and increased levels of ghrelin (which stimulates appetite). Basically, your cravings are controlled when you sleep. Other activities that occur when you sleep include skin repair and rejuvenation, toxins being flushed, your heartbeat slows, and blood pressure drops.