Surfing internet before sleep. Scientists found bright light exposure increased insulin resistance compared to dim light exposure in both the morning and the evening. In the evening, bright light also caused higher peak glucose (blood sugar) levels. Credit: © Sergey Nivens / Fotolia
Northwestern scientists found bright light exposure increased insulin resistance compared to dim light exposure in both the morning and the evening. In the evening, bright light also caused higher peak glucose (blood sugar) levels. Over time, the excess blood glucose could result in increased body fat, weight gain and a higher risk for diabetes. “These results provide further evidence that bright light exposure may influence metabolism,” said Prof. Kathryn Reid.
Previous research by Northwestern scientists showed that people who received the majority of their bright light in the morning weighed less than those who were exposed to most of their bright light after 12 p.m. The researchers wanted to understand why. Mouse studies also have shown that mice kept in constant light have altered glucose metabolism and gain weight compared to control mice.
The aim of the Northwestern study was to examine the acute effects of 3 hours of morning or evening blue-enriched light exposure compared to dim light on hunger, metabolic function and physiological arousal.
Method: 19 healthy adults were randomized to 3 hrs of blue-enriched light exposure starting either 0.5 hours after waking (morning group) or 10.5 hours after waking (evening group). Each person’s results were compared to their dim light exposure results as a baseline. The morning group ate breakfast in the light; the evening group ate dinner in the light.
Results: blue-enriched light exposure acutely altered metabolic function in both the morning and the evening compared to dim light. While morning and evening blue-enriched light exposure both resulted in higher insulin resistance, evening blue-enriched light led to higher peak glucose. This suggests a greater inability of insulin to adequately compensate for the increase in glucose in the evening. http://www.northwestern.edu/newscenter/stories/2016/05/web/bright-light-alters-metabolism.html
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