Researchers at Ohio State University have discovered a new risk factor obesity. It is exposure to light at night times. Experiments done on laboratory mice found that those dim-light exposure for eight weeks resulted in more than 50 percent weight gain in them when compared to mice which had normal exposure to light-dark cycle.
The results of the study are published in the October 2010 online edition of the journal the Proceedings of the National Academy of Sciences. It was funded by the National Science Foundation and the U.S.-Israel Binational Science Foundation.
How Dim-Light Exposure Can be a Risk Factor Obesity?
- Though there is no difference in the amount of food taken and in physical activity levels, mice exposed to dim-light continued to gain weight.
- Even there was no difference in the levels of a stress hormone corticosterone closely associated with metabolism in these mice.
- This lead the researchers to believe that light exposure affected the body metabolism in some ways.
- To gain further insight, mice were kept in three different lighting conditions, 24 hours of constant exposure to light, a standard light-dark cycle and low exposure to light.
- Amount of food consumed daily, the physical activity levels and body mass index of these mice were calculated every week.
- Results found that mice exposed to low light gained 12 grams weight in total beginning from the very first week and those mice exposed to standard light-dark cycle gained 8 grams of weight.
- Mice in the former group of mice were found hve higher levels of a fat epididymal and disrupted tolerance to glucose suggesting onset of diabetes.
- These experimental mice are supposed to eat more at night times. But the low light exposure mice ate 55 percent more at day times compared to 36 percent food intake of normal light-dark cycle mice.
- This development confirmed that the timing of eating gets disrupted by low light exposure and also has a major role to play in developing obesity.
- The researchers believe that metabolism is changed by low light exposure by bringing changes in the levels of a hormone (or signalling molecule) melatonin.
- Genes which control the body’s internal clock also might get altered bringing changes in the timings of eating.
Significance of the Research on Dim-Light Exposure As a Risk Factor Obesity:
The study suggests that late night exposure to light is a less known risk factor for obesity epidemic in the United States. Eating at wrong time is equally responsible for developing obesity and pre-diabetic status. Combined to a sedentary life style, watching television and sitting before computer for long at times can increase the risk level further.
