Written by Dr. Anitha Paderla, MBBS | 
Medically Reviewed by dr. reeja tharu, M.Phil.,Ph.D on Jul 28, 2021

Overview and Definition

Sleep is the golden chain that ties health and our bodies together. - Thomas Dekker -1572 - 1632

Sleep is natural to all living beings. It signals the cessation of physical activity and heralds the hours of rest. Akin to other needs of the body such as food, water, and warmth, sleep is a blissful state of inactivity and unawareness that provides the required rest and rejuvenates an individual for the activities of the ensuing day with increased vigor.

Every living creature goes through phases of sleep and wakefulness. The simplest answer to why we sleep is because we get tired and we cannot function if we get too sleepy.

When man was created, he came with an internal or biological clock, which controls the timings of the wakefulness-sleep cycle. This clock, which is sensitive to light, had evolved over the ages in close approximation to the 24hr light-dark cycle (circadian rhythm). Our ancestors followed the sunrise and sunset routine and had regular sleep schedules. Then came Thomas Alva Edison, whose invention of the electric bulb tampered with the signals received by the internal clock, setting our sleep and its pattern in disarray.

Make sure that you get enough sleep every day because lack of sleep can increase appetite, contributing to overeating and weight gain. Hormones that regulate appetite are influenced by sleep duration.


  1. Huxley, Aldous. In Coren S. Sleep Thieves: An Eye-Opening Exploration into the Science and Mysteries of Sleep. New York: The Free Press; 1996, p. 175.

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