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"Light Snacking" -- The Discovery Files

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Researchers at The Ohio State University found that mice that were persistently exposed to light at night exhibited 50% more weight gain, even when holding their physical activity and eating habits constant, than counterparts who were not exposed to light at night.

Credit: NSF/Karson Productions

Audio Transcript:

Lighten Up in the Dark.

I'm Bob Karson with the discovery files -- new advances in science and engineering from the National Science Foundation.

Could too much light at night lead to obesity? A study at Ohio State University found some interesting correlations between the amount of light at night and weight gain in mice.

(Sound effect: mice) Several groups of mice were tested each with equal activity levels and identical amounts of food. The only difference was varying light conditions. The mice who had dim light at night for eight weeks grew 50% fatter than mice who had regular light-in-the-day, dark-at-night conditions.

A second experiment was conducted with one difference: instead of the mice being able to access their food anytime, the food was restricted to a mouse's regular eating times. The result: no weight gain.

The study pointed to the times when the mice ate as the culprit in weight-gain. Although the dim-light-at-night mice didn't eat more than others, they did change when they ate and that affected metabolism. The dim light could have disrupted levels of melatonin -- a hormone that helps regulate metabolism. And it might have thrown off the mice's genetic clocks -- that control when they feed.

Light at night may contribute to weight gain in ways we don't expect, and it may explain why people who have good energy levels and low caloric intake still seem to gain weight. It could be in the timing.

But I'm still not cutting back on these candlelight dinners.

For the discovery files, I'm Bob Karson.

"The Discovery Files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at or on our podcast.

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