The release of hormones by the pituitary gland (the "master gland" of the endocrine system) is significantly affected by lack of sleep. Researchers have found that after several days of partial sleep loss, early evening cortisol ("stress hormone") levels are much higher and take six times longer to decrease before habitual bedtime. There is a domino effect between hormone imbalance, lack of sleep, and the impaired production of "ghrelin" and "leptin," the hormones that work together to regulate your appetite. After only one day of sleep restriction, studies have found that ghrelin ("hunger") levels are markedly higher, while leptin ("satiety") levels are markedly suppressed. When you are chronically tired, you also feel ravenously hungry because your body is playing tricks on your brain! When you have chronic lack of sleep, it also disrupts glucose and insulin metabolism, leading to a condition called "leptin resistance," when your brain can no longer "read" the signals of fullness from the leptin in your body. This leads you to overeat, since you are unable to recognize when your body is "full." More  studies are proving that chronic sleep loss causes weight gain, and there is also evidence that sleep loss weakens the immune system. Believe it or not: 40 percent of American adults get less than seven hours of sleep! How To Get Started Now: Go to bed early -- around 9pm is ideal -- and aim for 7 to 8 hours of sleep. If you're having trouble sleeping, make sure to create a calm bedtime routine, keep lights low, avoid stimulants like caffeine, and turn off all your electronic devices (TV, phone, computer) at least half an hour before sleep. If you're dealing with chronic sleep issues, a hormone imbalance could be the culprit. Get all your hormone levels checked (including melatonin if you're over 50) to determine the problem.