Obesity

Can Dim Light Exposure at Night Be a Risk Factor Obesity

Researchers at Ohio State University have discovered a new risk factor obesity; exposure to light during the night. Experiments done on laboratory mice found that those exposed to constant dim-light for eight weeks resulted in more than 50 percent weight gain when compared to mice which had exposure to a more normal daily light to 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 Bi-National Science Foundation.

Details of the Study

  • Even with no difference in the amount of food taken and in physical activity levels, mice exposed to dim-light tended to continue to gain weight.
  • The stress hormone corticosterone, which is closely associated with metabolism, was seen in the same amounts in both groups of mice.
  • Researchers have been led to believe that light exposure affected the body metabolism.
  • 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 were found to have higher levels of fat tissue in the body, and disrupted tolerance to glucose, suggesting onset of diabetes.
  • The experimental mice are expected to eat more at night times. The low light exposure mice ate 55 percent more at day times when compared to 36 percent food intake of normal light-dark cycle mice.
  • Developments 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 signaling molecule) melatonin.
  • Genes that 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. When combined with a sedentary life style, lack of nutritional education and lowered motivation, risk for becoming obese and developing related health diseases is increased.

References

Ohio State University: Too Much Light at Night May Lead to Obesity
http://researchnews.osu.edu/archive/lanmice.htm

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