(CORDIS) — 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.