Sun Exposure, artificial light and weight control. Marc Sorenson, EdD… Sunlight Institute
Sun exposure gives life and has so many positive effects, including anticancer, anti-heart disease, and anti-osteoporosis. Unnatural light, however can do exactly the opposite. In the case of obesity, artificial light at night (ALAN) can lead to weight gain, according to a study in the International Journal of Obesity.
The hormone melatonin works in conjunction with serotonin during each daily physiological cycle, known as the circadian rhythm. Serotonin is a natural “upper” that awakens our senses and prepares us for our workday. Then, when the rhythms are properly synchronized, as evening comes, serotonin decreases and melatonin, a sleep inducer, takes over so that we can sleep soundly and awake refreshed as daylight and serotonin once more take over. However, a monkey wrench is often thrown into the works. It is called artificial light at night (ALAN), and it may be one of many factors that lead to obesity. ALAN inhibits melatonin production, a factor in both obesity and cancer.
The researchers looked at satellite images of 80 countries, assessed the amount of ALAN emitted from each country and then compared the rates of obesity in each. The data was adjusted to take into consideration the differing dietary patterns in each country, as well as the urban vs rural population and other factors that would influence obesity.
The results showed, that after all adjustments, ALAN emerged as a prominent predictor for obesity.
So how does this relate to sun exposure? One of my recent posts noted the results of research on early morning sun exposure and obesity, noting that early sun exposure inhibited obesity dramatically. So not all light is good. Light at night is harmful; early morning sun exposure is wonderful. And if one wants to remain slim, it is imperative to eschew junk food, exercise and get plenty of non-burning sun exposure.
 Rybnikova NA, Haim A, Portnov BA. Does artificial light-at-night exposure contribute to the worldwide obesity pandemic? International Journal of Obesity. Int J Obes (Lond). 2016 May;40(5):815-23.
 Reid KJ, Santostasi G, Baron KG, Wilson J, Kang J, et al. Timing and Intensity of Light Correlate with Body Weight in Adults. PLoS ONE 2014 9(4): e92251. doi:10.1371/journal.pone.0092251