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To explore this connection, researchers analyzed U.S. military
satellite images of nighttime illumination around the globe and
country-level data from the World Health Organization (WHO) on the
prevalence of overweight and obese people.
Artificial light at night contributed to excessive weight in men and
women about as much as eating junk food, the research team reports
in the International Journal of Obesity.
“Because of artificial light at night, we often eat in the wrong
time, that is, after the natural dusk, when metabolic processes slow
down,” said N.A. Rybnikova of the University of Haifa in Israel.
The study doesn’t prove light bulbs cause obesity, and scientists
aren’t yet certain how lamps or the glow from gadgets like tablets
and televisions might influence how much people weigh, researchers
caution.
But it’s possible artificial light might contribute to obesity by
suppressing the production of melatonin, a hormone that helps
regulate sleep cycles.
These lights may also contribute to what’s known as social jet lag,
or disruption of the body’s natural circadian rhythms that happens
when people sleep and wake at times that are at odds with their
internal biological clocks.
For women and men, higher birth rates appear to be one of the
stronger predictors of excess weight and obesity.
Urbanization, as well as calorie intake of oils, fats and
carbohydrates also appear to predict excessive weight in men and
women alike. Consuming more roots and tubers was linked to a lower
likelihood of excessive weight, the study also found.
Together with variables like eating habits and exercise levels,
nighttime light explains up to about 73 percent of the variation in
rates of excess weight and obesity in women and up to 68 percent in
men, the study found.
The researchers also calculated overweight and obesity prevalence
for different levels of “Artificial Light-at-night,” or ALAN, using
a scale of zero to 1,000 ALAN (the highest observed level in 2010).
They found that overweight and obesity rises with ALAN intensities,
by 250 percent in most countries and 900 percent in Asia, at the
highest light levels compared to the lowest.
The study builds on earlier research linking excessive weight to the
use of tiny screens and other sources of light in bedrooms at night,
the authors note.
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“The evidence that exposure to artificial light at night is
associated with metabolic disturbances is continuing to accumulate,”
said Laura Fonken, a researcher at the University of Colorado who
wasn’t involved in the study.
“Overall, it seems that there aren’t any downsides to trying to keep
a consistent sleep schedule and avoid nighttime light exposure,”
Fonken added by email.
Just turning off smartphones and tablets and dimming the lights at
night probably won’t help with weight loss, cautioned Illa
Karatsoreos, of the Sleep and Performance Research Center at
Washington State University in Pullman.
“But if these things are disrupting your normal patterns of sleep,
and disrupted sleep is contributing to the problem, then these steps
would help,” Karatsoreos, who wasn’t involved in the study, added by
email.
“Anything to improve one's 'sleep hygiene' like reducing light and
noise at night should help improve sleep quality, and this may help
your body work more efficiently,” Karatsoreos added.
“We seem to be finally waking up to the realization that disrupted
sleep and biological rhythms are associated with many health
problems, including metabolic disruption, obesity, and
cardiovascular disease,” Karatsoreos said.
SOURCE: http://bit.ly/1P20TOg International Journal of Obesity,
online February 23, 2016.
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