How Sunlight Affects Sleep, Hormones and Body Fat

Since the beginning of human history, people have lived and worked outdoors during the light of day, absorbing light energy from the sky. An average of 10 hours outdoors each day, 70 hours weekly, was common.

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Following the advent of Edison’s long-lasting light bulb, over the last 100 years, people have moved indoors, away from the natural light that so faithfully regulated our circadian rhythms and energized our brain cells and bodies.

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Today, we spend an average of less than 30 minutes a day or a mere 3 hours per week in daylight, according to a study by Daniel Kripke, M.D., professor of psychiatry at UC San Diego. Scientific research has proven that our circadian rhythms are dependent upon light entering our eyes to regulate our body’s master clock. According to the quality and quantity of light received, key hormones and neurotransmitters like serotonin and melatonin are released in the brain to set our daily rhythms.

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Is it any wonder that we experience many of the symptoms of being out of rhythm? Weight gain, fatigue, depression, headaches, pain, hormonal imbalances, sleep disorders, PMS, lowered immune responses, vitamin deficiencies and lack of vitality are but a few of the many health problems that may be associated with being out of rhythm.

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Artificial Light and Obesity

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Since low fat diets and exercise have gone to war against obesity, the average American has actually gained 8.5 pounds. Increasing numbers of people are getting type 2 diabetes. Some people feel they exercise like maniacs but are always hungry, are overweight and gain weight if they even smell a cookie.

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Researchers T.S. Wiley and Bent Formby believe that the over consumption of fat and a lack of exercise do not cause obesity, heart disease, diabetes and cancer. They base their conclusions on more than a decade of research at the National Institutes of Health. They say that avoiding artificial fats can help, but completely avoiding artificial toxins is impossible. They believe the problems of obesity and cancer can be helped with a solution as simple as turning off a light bulb and paying more attention to the essential need for sunlight.

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Before the invention of the light bulb and the electric power grid, when the sun set, the environment grew dark. If people stayed up late, their activity was lit by the dim glow of fire or candles. When night fell, most people went to bed and slept. In the winter, people spent up to 14 hours a day in the dark. In the past, the abdominal fat pad now common year-round in insulin-resistant and type 2 diabetic patients would have kept internal organs warm and served as an energy store for the famine season of winter.

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In cold weather, the body increases cholesterol production to lower the freezing temperature of cell membranes. Chronic high insulin leads to insulin resistance. Blood sugar cannot enter muscle cells, so all sugar goes to fat cells for storage or gets turned into cholesterol. This makes insulation and “antifreeze” to prepare the body for the winter famine that never comes for many in the modern world. In the summer, the body gets the message to produce hormones that say, “Eat all you can and build up a fat pad so you will survive the dark winter famine.” The readily available annual supply of sugary foods at anytime during the day or night contributes to the hormone disruption cycle.

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Today, artificial light tricks the body into thinking every day, year-round, is the season to eat a lot and gain weight. Moreover, the flickering light of TV at night causes dopamine release telling the body to eat and store fat. Even if one sleeps eight hours a night, several hours may be spent sleeping in a room with artificial or outside light leaking in, interfering with melatonin production.

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Artificial light also provides an abnormal light spectrum. Staying up late also means insulin stays higher at night, when it should be low. Cortisol levels then fall so late that they interfere with deep sleep, and then cortisol does not come up normally in the morning. If cortisol is not high enough to enhance dopamine release in the morning, a person may feel rushed and have poor memory and trouble planning for the new day. Abnormal cortisol fluctuation can also cause the appetite to come roaring on in the afternoon and evening. Melatonin would have suppressed the appetite at night, but it will not be available to do so when the lights are on.

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Thus, after sunset, the later we have exposure to light bulbs, computer monitors, and TV screens, the more we are prompted to eat, especially carbohydrates. It doesn’t work to try to burn off the extra weight through exercise at night because that makes the cortisol levels go up even more.

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The natural hours of light and dark each day regulate hormones like insulin, serotonin and dopamine. Light curbs melatonin production at the pre-optic site connecting to the pineal gland. Research on rats showed that light, even less than that of a candle, in the dark phase (night), disrupts the production of the antioxidant melatonin and increases tumor growth. On the other hand, long dark nights change the metabolism from sugar burning to fat burning.

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Artificially long hours of light—every day, all year long—eliminate seasons, as far as the body can tell. This can be countered by reducing the amount of light in one’s environment at night and by getting adequate sunlight for good light hygiene.