Lack of sunlight may increase your weight during the winter period for different reasons

Lack of sunlight may increase your weight during the winter period for different reasonsScientists from Alberta University in Canada have observed that lack of sunlight may contribute to the weight increase that many people experience during the winter period. This is because our fat cells are sensitive to sunlight. Lack of sunlight may also result in poor sleep and low levels of vitamin D, a nutrient that has other metabolic functions.

The sun and the other stars radiate light in different colors (also known as wavelengths). The shorter the wavelength, the bluer the light. Longer wavelengths make light redder. Yellow light is somewhere in between. A rainbow clearly shows the shift between wavelengths and their colors. Some wavelengths such as UV-rays are even shorter, and radio waves are even longer. We are unable to see either of the two.

Blue wavelengths make fat cells store less fat

As the sun climbs higher in the sky and spreads its light, the blue wavelengths increase in strength and are able to penetrate our skin and reach the fat cells underneath. This shrinks the fat particles in the cells and causes them to leave the cell. According to Professor Peter Light (!!), who headed the study, this observation shows that sub-cutaneous fat cells are not able to store as much fat when they are exposed to blue wavelengths.
On the other hand, there are eight months every year where, at northern latitudes, the sun sits low in the sky or is completely absent. A lack of powerful light and blue wavelengths may cause us to store more fat during the winter period and gain 2-3 kilos, even with unchanged diet and exercise habits. Most probably, humans in our parts of the world were originally “engineered” to gain a few pounds to protect themselves against the cold during winter. However, it is not desirable for modern man, who tends to be slightly overweight, to begin with.

Blue light as new therapy

According to Peter Light, these studies are only preliminary. Exaggerated sunbathing, anyhow, can be bad for your health, so it is not something people should pursue to lose weight. Still, the new discovery may pave the road for new science where light therapy is used to treat overweight and related diseases such as diabetes.
According to Peter Light, the blue wavelengths may even influence the number of fat cells that we produce in our childhood, and which stick with us the rest of our lives. Some research and statistics predict that the coming generations will be increasingly overweight, even with all the focus there is on diet and exercise. Then again, we do need sunlight for the benefit of our health.

The biological clock of our skin

The researchers made their discovery as part of an attempt to help patients with type 1 diabetes. They studied how genetically engineered fat cells managed to produce insulin in response to light. As Peter Light sees it, their discovery was somewhat unexpected. He now assumes that the fat cells of human skin work like a biological clock of some kind.
It has been known for some time that the biological clock in our bodies is “kick-started” by the blue wavelengths from the morning sun. There is a direct nerve connection from the retina of the eye to the pineal gland in the brain, which produces serotonin in the daytime to keep us fresh. Therefore, we need plenty of daylight. In contrast, the diminishing, reddish evening light and the darkness at night signals us to go to sleep. The body then converts serotonin to melatonin, a “sleep hormone” that ensures a good night’s sleep and healthy dream activity.
Just for the record, three American scientists were awarded the Nobel Prize in Physiology in 2017 for discovering the molecular mechanisms that control our circadian rhythm and the ticking of the inner clock inside our cells.

Avoid blue LED light at night

Nature did not intend for us humans to be exposed to artificial light at night, as this may affect the body in the same way as sunlight by telling us that a new day is beginning. This makes it difficult for the body to synthesize the melatonin we need to fall asleep. The more recent light types such as LED energy saving bulbs and light from smartphones and electronic gadgets are a problem, as they omit a stronger blue light. We tend to sit up late working at the computer or, worse yet, bring our phones, tablets, and computers with us to bed. Studies show that too little sleep may disturb our blood sugar balance and cause us to store more fat.

If you want to improve your melatonin production and your sleep

  • prioritize red or yellow light in the evening. For instance, use special glasses that block the blue light. Another option is to take a melatonin supplement.

Lack of sunlight and vitamin D contributes to weight gain and obesity

During the summer period when the sun sits sufficiently high in the sky, UV rays enable our skin to synthesize vitamin D that has many functions in the metabolism. Lack of vitamin D is very widespread, especially during the winter period, and overweight people and individuals with type 2 diabetes tend to be deficient in the nutrient. A study from Baylor College of Medicine in Houston, Texas, showed that the relation between overweight and the lack of vitamin D is rooted in the brain, from where vitamin D normally contributes to the regulation of weight and blood sugar.


Katarina Ondrusova et al. Subcutaneous white adipocytes express a light sensitive signaling pathway mediated via a melanopsin/TRPC channel axis. Scientific Reports 2017

University of Alberta Faculty of Medicine & Dentistry. New discovery may explain winter weight gain

Hanne Kokkegård. Døgnrytmens mekanik udløser Nobelprisen i fysiologi. Ingeniøren okt. 2017

Sisley SR et al. Hypothalamic Vitamin D Improves Glucose Homeostasis and Reduces Weight. Diabetes 2016

Graven, Andreas R. Søvn påvirker vægt og aktivitetsniveau. 2014

Pierpaoli Walter, Regelson William. The Melatonin Miracle. Simon and Schuster 1996

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