Electric light has long allowed us to work, rest and play 24/7, defying
the Earth’s natural rotations that define night and day. But when Thomas Edison
tested the first light bulb in 1879, he probably didn’t imagine that his
invention could one day contribute to a global obesity epidemic.
But now, a new paper from a
researcher based at the University of Aberdeen in the United Kingdom suggests
just that. Writing in the journal BioEssays, Dr Cathy Wyse, from the university’s
Institute of Biological and Environmental Science, presents the results of her
research into the effect artificial light cycles have on our health, and more
specifically on our weight.
Our daily sleep-wake cycle is
controlled by a molecular clock present in every cell of the human body. It has
its own inbuilt default rhythm of almost exactly 24 hours, allowing it to stay
finely tuned to the daily cycle generated by the rotation of the Earth.
But in our modern world, the
human clock struggles to stay in tune with the Earth’s daily rotation cycle:
exposure to artificial light cycles, and the developed world’s irregular meal,
work and sleep times are the culprits. Researchers refer to this imbalance
between the natural circadian rhythms of our bodies and the environment as the
‘circadian desynchrony’, and Dr Wyse believes it is a contributing factor to
the planet’s bulging waistlines.
‘The reason for the relatively
sudden increase in global obesity in the developed world seems to be more
complicated than simply just diet and physical activity. There are other
factors involved, and circadian desynchrony is one that deserves further
attention,’ explains the researcher.
Her study explores how circadian
desynchrony affects human health by disrupting the systems in the brain that
regulate metabolism, leading to an increased likelihood of developing obesity
and diabetes.
Dr Wyse continues: ‘Electric
light allowed humans to override an ancient synchronisation between the rhythm
of the human clock and the environment, and over the last century, daily
rhythms in meal, sleep and working times have gradually disappeared from our
lives. The human clock struggles to remain tuned to our highly irregular lifestyles,
and I believe that this causes metabolic and other health problems, and makes
us more likely to become obese.’
As the human clock is controlled
by our genes, the study suggests that some people may be more at risk of the
effects of circadian desynchrony than others. For example, humans originating
from Equatorial regions may have clocks that are very regular, which might be
more sensitive to the effects of circadian desynchrony.
Dr Wyse based much of her work on
studies of microbes, plants and animals that show synchronisation of the
internal clock with environmental rhythms is important for health and survival;
it is highly likely that this holds true for humans as well.
Although changing work patterns
and 24-hour lifestyles have become staples of today’s developed world, healthy
circadian rhythms can be maintained by keeping regular meal times, getting a
good night’s uninterrupted sleep in complete darkness, and by getting plenty of
sunlight during daylight hours.
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