Shining a Night Light on Obesity

f you're wishing upon a star in hopes to stop packing on the pounds, you might already be jinxing yourself. A recent study finds that continual exposure to light at night may lead to weight gain, even without changing physical activity or eating more food. Researchers say that instead of wishing upon the stars . . . maybe you should sleep under them.

Researchers found that mice that were exposed to a moderately dim light at night over eight weeks had a body mass that was around 50 percent more than other mice that lived in a standard light-dark cycle. "Although there were no differences in activity levels or daily consumption of food, the mice that lived with light at night were getting fatter than the others," which Laura Fonken, lead author of the study and a doctoral student in neuroscience at Ohio State University, was quoted as saying.

The study revealed that the mice living with light at night eat at times they normally wouldn't, which is a main factor of their weight gain. One study showed that mice exposed to light at night -- but with food restricted to normal eating times -- gained no more weight than did mice in a normal light-dark cycle.

"Something about light at night was making the mice in our study want to eat at the wrong times to properly metabolize their food," which Randy Nelson, co-author of the study and professor of neuroscience and psychology at Ohio State, was quoted as saying. If these results are confirmed in humans, it would verify that late-night snacking is a possible risk factor for obesity.

In another study, mice were housed in one of three condition: 24 hours of constant light, a standard light-dark cycle (16 hours of light at 150 lux, 8 hours of dark), or 16 hours of daylight and 8 hours of dim light (approximately 5 lux of light).

Researchers measured the amount of food the mice ate each day, in addition to how much they moved in their cages each day using an infrared beam crossing system. Furthermore, body mass was calculated each week. Compared to mice in the standard dark-light cycle, mice that were exposed to dim light at night showed notably higher increases in body mass, beginning in the commencement of the study and continuing to end.


Light-at-night mice had gained 12 grams of body mass by the end of the experiment, compared to 8 grams for those in the standard light-dark cycle. It was reported that mice in constant bright light additionally gained more than those in the standard light-dark cycle; however the scientists stated that the dim light-at-night mice were better comparisons to the light exposure human generally are exposed to.

What's more, the dim light-at-night mice showed higher levels of epididymal fat as well as impaired glucose tolerance - a marker for pre-diabetes...