Exposure to artificial lighting at night can cause obesity

From the new study, conducted at the Ohio University in Columbus in collaboration with Prof. Avraham Haim from the University of Haifa, it became clear that obesity is not related to the amount of food or physical activity, but to the time when you eat

Exposure to artificial lighting at night can cause obesity, regardless of the amount of food or physical activity, according to a new study conducted at Ohio University in collaboration with Prof. Avraham Haim, head of the Center for Chronobiology at the University of Haifa. "If until now we have found a connection between artificial lighting and cancer, now we are finding additional negative effects of artificial lighting - a cause of environmental pollution that is spreading like wildfire," said Prof. Haim. The research, funded in part by the Israel-United States Binational Science Foundation, was published in the early electronic edition of the prestigious journal Proceedings of the National Academy of Science (PNAS).

Following the spread of the phenomenon of obesity in the world, much emphasis was given to factors such as improper eating and a lack of sports activity. Recently, however, researchers began to find a connection between damage to the body's cyclical actions, which are regulated by the biological clock, which is adjusted every day by cyclic timers such as sunrise and sunset, and obesity. According to Prof. Haim, since exposure to artificial lighting at night cancels the natural setting of the sun, we continue to be exposed to high lighting intensities that disrupt the direction of the biological clock and thereby impair the cyclical activity of cells, tissues, organs and systems. Therefore, the researchers wanted to examine these disruptions in the context of the phenomenon of obesity in industrialized countries. The one who led the research team was Laura Funken, a doctoral student in the laboratory of Professor Randy Nelson in the Department of Neuroscience at Ohio State University.

In the first part of the current study, the researchers compared three groups of laboratory mice. One group was exposed to a "normal day": 16 hours of light and eight hours of darkness. Another group was exposed to light for 24 hours continuously. A third group was exposed to normal light for 16 hours and dimmed light for 8 hours. The three groups were exposed to these conditions for 8 weeks and the same amount of food.

The findings show that the dimmed light group and the group exposed to 24 hours of light increased their body weight by approximately 12 grams, compared to approximately eight grams by the "normal day" group, which is a difference of approximately 50% of the change in mass between the groups. It also turned out that there was no difference in the amount of food the mice ate or in their level of activity during the day. It was also found that the level of glucose tolerance decreased significantly in both groups that were exposed to light at night.

Another finding, which led to the second part of the study, showed a significant change in the time of food consumption: the mice exposed to the "dimmed day" ate 55% of their food during the "night" (actually, dimmed light) while the mice exposed to the "normal day" ate only 36.5 % of food at night. Therefore, the researchers checked whether the change in food consumption times is the one that leads to the significant differences in weight gain in body mass. To this end, the "normal day" and "dark day" mice were allowed three options: the possibility of unlimited eating; eating only during the day; Eating only during the night (there was no point in this experiment to examine the mice of the third group because they did not have any night). From the findings it became clear that once they limited the eating to only the day - the time when the mice eat normally - or only to the night - a time when the mice are not used to eating - there was no difference in the increase in body mass between the groups.

According to Prof. Haim, the findings of the study confirm the findings of other studies, that exposure to artificial lighting at night causes a prevention in the production of the hormone melatonin in the pineal gland in the brain. The explanation is that it is this disorder that brings about changes in the body's cyclical activity system and causes the mice to eat at times they are "not supposed to" eat. "This study shows that indeed sitting in front of the television at night can cause obesity, but not only because of lack of activity and overeating, but also because of the disruption of the daily cycle. It has already been said in the book of Ecclesiastes (chapter XNUMX) that 'for every time, and every season for every thing under heaven'. With the help of Edison's technology, we 'eliminated' the darkness, but in fact we created a new pollution from an environmental point of view, which originates from damage to the environmental time variables," said Prof. Haim.

His conclusion is not to "turn off the light" and return to the days before Edison, but to be aware of the problem and the pollution resulting from artificial lighting and to prepare properly, through comprehensive studies, as is starting to happen in countries with high environmental awareness.