Exposing mice to light at night disrupts their meal times, causing them to put on weight.
Laura Fonken at Ohio State University in Columbus and her colleagues report that mice exposed to 24 hours of continuous light, or 8 hours of low light overnight, gained significantly more weight and were less tolerant to glucose than mice receiving the standard 8 hours of night-time darkness. All mice had the same levels of caloric intake and daily activity.
Mice are nocturnal creatures that typically eat more at night. But those kept under dim light at night ate more than half of their food during daylight hours, compared with little more than one-third for mice under standard conditions. The authors suggest that the weight gain of mice exposed to night-time light occurred because their food intake became desynchronized from their metabolic cycles.
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Metabolism: Night light, weight gain. Nature 467, 887 (2010). https://doi.org/10.1038/467887b
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DOI: https://doi.org/10.1038/467887b
