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Light at Night May Contribute to Weight Gain


If you tend to stay up late and are exposed to light at night, whether it be the glow of a computer or TV screen or a reading lamp, your habit may contribute to weight gain. Researchers found that mice that lived with light during nighttime hours put on weight even when their food intake did not increase.

Weight gain may be linked to night light

In the new study, the results of which were published online in Proceedings of the National Academy of Sciences, researchers discovered that mice exposed to dim light at night over two months gained 33 percent more weight than mice that were exposed to a normal light-dark cycle. The weight gain occurred even though all the mice maintained the same activity level and food intake.

The difference between the two groups of mice, according to Laura Fonken, a neuroscientist at Ohio State University, and her colleagues, is that the mice exposed to night light ate at different times. Professor Randy Nelson, one of the study’s co-authors, noted that “light at night is an environmental factor that may be contributing to the obesity epidemic in ways that people don’t’ expect.”

Previous studies have indicated that shift workers are more susceptible to heart disease and diabetes, and that these risks may be associated with weight gain. In a recent study published in Nutrition Research Reviews, for example, investigators reported that in developing countries, overweight and obese individuals are more prevalent among shift workers than day workers, and that shift workers seem to gain weight more often than their day worker peers.

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The investigators concluded that “there is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes and CVD [cardiovascular disease], perhaps as a result of physiological maladaptation to chronically sleeping and eating at abnormal circadian times.”

Regarding the mouse study, Nelson pointed out that “something about light at night was making the mice in our study want to eat at the wrong times to properly metabolize their food.” Yet when the researchers limited food intake to times when the mice would normally eat, weight gain did not occur.

Nelson suggested that people who often use a computer and watch TV at night may be disrupting their metabolism by eating at abnormal hours. “This environmental factor may explain why some people who maintain good energy balance still gain weight,” he said.

If the results of this study are verified in humans, people who want to ward off weight gain may want to turn off the night light and eat at regular hours.

Antunes LC et al. Nutrition Research Review 2010 Jun; 23(1): 155-68
Proceedings of the National Academy of Sciences



I have never heard such nonsense in all my life.
Really, this is so hard for you to believe? What other mundane discoveries have you had trouble with? Smoking is bad for your health? Lack of sleep will make you tired? Tanning beds will give you skin cancer?