Circadian rhythms: Cycles such as the sleep-wake cycle that control body functions. Circadian rhythms are controlled by a “biological clock” in the brain, which is regulated by light and darkness.
Cortisol: “Stress hormone” released from the adrenal glands. Inadequate sleep causes an increase in cortisol. When cortisol is too high for too long, it can increase belly fat and interfere with metabolism (such as the way your body converts calories from food into energy).
Ghrelin: “Hunger hormone” released from cells in the stomach. Inadequate sleep causes an increase in ghrelin and feelings of hunger.
Hunger: Feelings of discomfort coupled with the desire to eat, often caused by low blood sugar.
Immunity: Body’s ability to resist infection.
Insulin: “Calorie-storage hormone” released by the pancreas. Insulin moves sugar out of the blood into cells, where it is burned for energy or stored for later use.
Insulin resistance: A condition that happens when cells in muscles, fat, and liver do not respond well to insulin, leading to elevated levels of blood sugar. Insulin resistance can lead to type 2 diabetes.
Leptin: “Satiety hormone” released from fat cells. Inadequate sleep causes a decrease in leptin and can lead to overeating.
Melatonin: “Sleep hormone” secreted by the pineal gland in the brain. The “biological clock” is regulated, in part, by melatonin. Exposure to light interferes with melatonin and can interrupt the timing of sleep.
Non-Rapid Eye Movement (NREM) sleep: “Quiet” sleep during which blood supply to the muscles is increased, energy is restored, tissue growth and repair occur, and hormones are released for growth and development.
Rapid Eye Movement (REM) sleep: “Active” sleep during which the brain is active and dreams occur. The body is immobile, heart rate and blood pressure increase, and breathing is irregular.
Satiety: State of feeling full after eating.
Sleep hygiene: A routine and sequence of behaviors that contribute to getting enough sleep each night.
Type 2 diabetes: A disease that develops when the pancreas cannot make enough insulin to overcome insulin resistance.
White noise: Steady, unvarying, and unobtrusive background sounds that mask or block out other sounds and can make it easier to fall asleep.