Before there was artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now of course, most people in the world spend their evenings in illumination. At night, light throws the body’s biological clock – the circadian rhythm – “out of whack.” And, blue wavelengths – which are beneficial during the day because they boost attention, reaction times, and mood seem to be the most disruptive at night. The snowballing of electronics with screens, as well as energy-efficient lighting is increasing our exposure to blue wavelengths, especially after sundown.

A new study suggests that blue-enriched light exposure right before and during the evening meal may increase hunger and alter metabolism.

“It was very interesting to observe that a single three-hour exposure to blue-enriched light in the evening acutely impacted hunger and glucose metabolism,” said study co-author Ivy Cheung, a doctoral candidate in the Interdepartmental Neuroscience program at Northwestern University in Chicago. “These results are important because they suggest that manipulating environmental light exposure for humans may represent a novel approach of influencing food intake patterns and metabolism.”

The research abstract was recently published in the journal Sleep.

Results show that blue-enriched light exposure compared with dim light exposure was associated with an increase in hunger that began 15 minutes after light onset and was still present almost 2 hours after the meal. Blue light exposure also decreased sleepiness and resulted in higher measures of insulin resistance…….   Harvard Health Publications  5/12     Science Daily   6/2/14


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