Nighttime Artificial Light Exposure Linked with Obesity and Hormone Changes

Linda J. Dobberstein, Chiropractor, Board Certified in Clinical Nutrition

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Nighttime Artificial Light Exposure Linked with Obesity and Hormone Changes
Long summer days with extended natural daylight provides a great time to get outdoors and is enjoyed by many. This is especially true for those of us here in the upper northern states. Contrast this natural light to artificial light at night that modern life has brought us over the last several decades. This change in light exposure has caused researchers across the globe to be seriously concerned about artificial light at night (ALAN). Several recent studies show that the chronic exposure to artificial light at night affects many bodily hormones and is a causative factor to the worldwide obesity epidemic. Some studies find other disorders like hormonal cancers linked with this artificial light exposure at night.

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The Nara Medical School in Nara, Japan recently published a study on ambient artificial light at night that is grabbing the media’s attention. These scientists looked at 1,100 elderly participants, average age 72 years, and followed them over the course of nearly two years. They evaluated numerous health and lifestyle factors. It was found that those individuals who had the most evening or nighttime exposure to artificial light were much more likely to have weight gain and increased waist size than those who did not have the same amount of ambient artificial nighttime light exposure. It was also noted that those who had the most morning exposure to natural light had healthier body weights and smaller waist size.

In this study, scientists found that people who were exposed to even a very small amount of light in the late evening and during the night had a higher likelihood of weight gain, especially around the waist. They came to the conclusion that increased nighttime light exposure was estimated to correspond to a 10.2 percent weight gain and a 10 percent increase in the BMI (body mass index) over 10 years. Those who consistently had bright light exposure early in the morning had the best results with healthier BMIs. This was regardless of calorie intake, physical activity and sleep-wake parameters.

Light and the Master Biological Clock


Light exposure influences the most fundamental and critical aspect of metabolism by affecting the body’s master biological clock. The balance and timing of energy and metabolism is maintained by a special group of nerve cells called the suprachiasmatic nucleus (SCN) found in the hypothalamus of the brain. This is the master biological clock. It sets the rhythm and timing for all of the rest of the clocks in body which includes leptin, insulin, and thyroid, etc. and several gene clocks.

Scientists are finding out that the ambient artificial light at night disrupts the rhythm of these internal clocks. The use of artificial light at night creates a circadian misalignment between internal body clocks and the natural environmental rhythms. This change in light settings becomes like an orchestra being conducted by several conductors. It creates a chaotic, noisy, anti-rhythmic sound. This disrupted rhythm has been shown to affect the nerve tissue organization in the central circadian pacemaker (SCN), along with changes of the waveform and amplitude of rhythm in electrical activity. It changes the plasticity and functionality of the body’s “grandfather clock” of the brain, and other clocks with organ, hormonal, and cellular rhythms.

Shift work, travel, and time zone changes, also play a role. Studies have revealed that these altered internal clock rhythms cause impaired glucose tolerance, decreased energy, obesity in humans and animals, reduced insulin response and function after glucose challenge, weight gain, decreased leptin levels, increased grehlin, and metabolic syndrome. One study even demonstrated that short sleep duration, i.e. getting 5 hours of sleep per night and the altered circadian clocks actually reduced the function of insulin by 20 percent. These changes reduced insulin sensitivity. Once sleep was restored to 9 hours per night for several days, insulin sensitivity improved back to baseline in healthy adults. It, however, took more than just a weekend of sleep and unaltered circadian rhythms to restore healthy baseline insulin function.

Global Effects of Light Exposure at Night


Other studies in recent months confirm that the increase in excess weight and obesity affects nearly 2 billion individuals on this planet and correlates with the outdoor ambient light exposure at night. A recently published population study looked at satellite images of night time illumination, combined it with several factors including obesity rates as reported by the World Health Organization (WHO). These authors found a statistically significant and positive predictor of obesity about 70 percent of the time in more than 80 countries worldwide. This was the first population study that confirmed and demonstrated ALAN is a significant contributing factor to obesity in the global human population.

Other studies agree and conclude “analyses showed that high outdoor ambient light at night exposure was significantly associated with obesity after adjusting numerous factors like age, sex, educational level, type of residential building, monthly household income, alcohol consumption, smoking, consumption of caffeine or alcohol before sleep, delayed sleep pattern, short sleep duration and habitual snoring.”

Nocturnal Artificial Light Exposure causes Hormonal Changes and Cancer


If you find that perhaps the obesity or metabolic syndrome concerns don’t apply to you, there is more to the story. Excessive artificial light at night has been suggested to be linked with cancer. One recent study suggests that the increased rates of breast cancer were found to be notably associated with artificial light at night exposure. This occurred because of the disruption in biorhythms and hormones after numerous factors were adjusted for. This association was found in breast cancer, but not other cancer types in women.

Men have similar concerns with increased prostate cancer associated with nighttime artificial light exposure. After a review of several world-wide databases and studies, researchers published an article earlier this year on this topic. Important statistical differences were found. The global burden of hormone dependent cancers like prostate and breast cancer has been linked with the increased use and prevalence of artificial light at night. Research has shown us that leptin, obesity, prostate cancer and breast cancer are linked. Add in the prevalence of nighttime artificial light.

Managing Modern Exposures and Leptin and Insulin Disruptions


Modern creature comforts and technology may be creating a more noxious effect to health than we could have ever imagined when the first light bulb came into existence. Short of planet wide destruction of all the artificial light we have become so accustomed to or completely living off the grid, we will not get rid of this ever-present factor. It does mean that we need to have judicious timing and use of artificial lights.

Open up the blinds or curtains or get outside first thing in the morning to help reestablish the natural daylight rhythms to the internal body clocks. Or use light bulbs that depict a higher lux in the morning like those used for Seasonal Affective Disorder. Reduce or eliminate the nighttime light exposure as much as possible. Go camping for a few days to reacquaint yourself to the natural day-night cycle and you will find your body getting back in sync with nature. Our bodies are wired for this natural rhythm. If technology and some bad habits are impeding your health, isn’t it worth turning off the computer, smart phones, and lights at an earlier hour?

These findings also mean that we cannot ignore artificial light exposure and how it affects leptin, insulin, obesity, and metabolic syndrome. We must make healthy choices in order for our bodies to have a chance at maintaining health in this challenging world. We may not be able to change the streetlights outside, but we can use black-out curtains and reduce/eliminate our own personal electronics exposure at night. If your job requires shift work or traveling, caring for loved ones in the middle of the night, or you’re a night owl by nature, and you want to get or keep leptin and insulin optimal. It is imperative to manage leptin.

Metabolism is All About Timing


Following the Five Rules of The Leptin Diet is fundamental. It is just as essential as the natural day-night rhythm. Metabolism is all about timing.

The Five Rules of the The Leptin Diet:
Rule 1: Never eat after dinner.
Rule 2: Eat three meals a day.
Rule 3: Do not eat large meals.
Rule 4: Eat a breakfast containing protein.
Rule 5: Reduce the amount of carbohydrates eaten.

Top Nutrients for Optimizing Strained Hormones


Many nutrients support healthy leptin and blood sugar function. This balance is essential for adults and children too. These include starting off your day with quality protein in adequate amounts or as a quick, easy protein smoothie. Adding fiber to a protein smoothie and as a regular part of your diet helps stabilize blood sugar swings and reduce insulin resistance.

If you have to work at night but find yourself reaching for high carb, high fat foods to curb the cravings or for energy, try a protein smoothie with fiber instead. Add some healthy oils to it and you will find yourself feeling very satisfied. Use nutrients like chromium, cinnamon, and green coffee berry extract to help healthy blood sugar and insulin. Standardized green tea extract and its active ingredient EGCG has some of the highest benefits for stabilizing blood sugar and reducing insulin resistance in type 2 diabetics especially when consuming a high fructose/ high sugar diet.

I wonder what Thomas Edison and other geniuses who studied and developed electricity would think of their ideas and inventions now. Their efforts have forever changed the world in countless ways. But at the same time, will we ignore the growing evidence that we need to be mindful of these factors and properly manage their timing and exposure or will we become the century known for displaced circadian rhythms, failing health, wishing we could turn back the hands of time?

Nutritional Support



Whey Protein – High quality whey protein provides all of the amino acids to the body without added sugar. Protein helps increase metabolism for up to 12 hours after intake. Optimizing protein intake is critical for healthy leptin function.

Chromium – This mineral is required to transport glucose into cells. This helps calories be burned more efficiently while supporting healthy insulin function. Modern agricultural practices and carbohydrate rich diets render this nutrient depletion. Exercise helps improve the function of chromium.

Cinnamon – This aromatic spice is especially powerful when in a special water soluble extract. It contains bioactive factors for healthy insulin function and powerful antioxidants.

Green Coffee Berry Extract – Green coffee beans contain an ingredient called chlorogenic acid. Chlorogenic acid is removed when coffee beans are roasted. This nutrient has been found to assist significantly with weight loss. It is a rich source of polyphenol antioxidants.

Green Tea Extract – This popular herbal compound has been shown to support healthy insulin, blood sugar, and leptin levels. Green tea quality matters as the delicate antioxidants are damaged with chemicals and solvents found common in cheap green tea.

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