Is Artificial Night Light Contributing to Obesity?

More and more data keeps rolling in to suggest that artificial night light may be contributing to the excess of obesity. The bluish light from our glowing rectangles seems to be a particular problem. As with most potential causes of obesity, resolving the question of causality is the key challenge. Two new studies are adding to the evidence for thinking the link might one of cause and effect.

In the International Journal of Obesity, Nataliya Rybnikova and colleagues published and an analysis of satellite imagery of global nighttime illumination and WHO (World Health Organization) data on obesity prevalence by countries, along with other demographic and health-related data. The authors concluded:

This study is the first population-level study that confirms the results of laboratory research and cohort studies in which ALAN [artificial light at night] was found to be a contributing factor to excessive body mass in humans.

In a randomized controlled study published by Chronobiology International, Masahiko Ayaki found that protective eyewear filtering out blue light from electronic devices for two hours before sleep at night had a significant effect on sleep quality and melatonin secretion compared to control eyeware. This finding supports other research, in which the blue light emitted by electronic devices at night has been shown to disrupt melatonin secretion and circadian rhythms, leading to sleep disruption and metabolic dysfunction.

These two studies are small pieces in a much larger puzzle that has been coming together for years. Sleep disruption is pretty clearly a factor in rising obesity rates. Artificial light at night is very likely a factor in this disruption.

So if it’s dark outside, maybe it’s time to shut off the glowing rectangles.

For the study in IJO, click here. For the study in Chronobiology International, click here. For more on the effects of artificial light at night on human health, click here.

Nature’s Nightlights, photograph © Susy Morris / flickr

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February 20, 2016