Could we solve the global obesity crisis by turning out the lights?


A provocative paper published Wednesday evening makes the case that the rising incidence of obesity worldwide may be linked to the disruption of our bodies’ circadian rhythms caused by the growing presence of artificial lighting.

Writing in the journal BioEssays, Cathy Wyse, a chronobiologist at the University of Aberdeen in Australia, explains that the human body, like those of other species, is governed by circadian rhythms, a set of mental, physical and behavioral changes designed to be finely tuned to the variations in natural sunlight and darkness throughout the day and night.

Circadian rhythms, which vary from person to person and likely have a genetic component, follow a 24-hour cycle. Their disruption has been tied to sleep disorders and some mental illnesses such as depression and bipolar disorder, according to this fact sheet from the National Institutes of Health.

The advent of artificial light in the late 19th century brought disruptions to circadian rhythms, exposing people to light at times of day when their bodily and mental functions expect darkness and causing what chronobiologists call “circadian desynchrony.” Artificial lighting also has made shift work more possible, which has in turn altered people’s sleep and eating schedules, Wyse notes.

Wyse notes that our increased exposure to artificial lighting has coincided with the rise of obesity. It’s possible, she suggests, that the disruption of our natural cycle has spurred changes in our bodies and minds that make us more vulnerable to weight gain. The associated shift in eating and sleep habits might exacerbate the situation, Wyse reasons.

In support of her argument, she cites research showing that groups of people who migrate away from equatorial zones, where periods of sunlight and darkness are highly regular, to latitudes where there’s greater fluctuation in daylight tend to be among those most susceptible to weight gain.

Okay, so let’s say Wyse is onto something here. What on earth – or on Earth – can we do about it?

In her paper, Wyse acknowledges, “Restoration of circadian resonance would entail abolition of shiftwork, and restriction or even elimination of light at night. Such radical changes to human lifestyle cannot be justified in the current absence of scientific evidence for a causative association between circadian desynchrony and metabolic dysfunction and obesity in humans.”

Still, she concludes, “Future studies should focus on understanding how the functional parameters of the human clock interact with a desynchronised environment to affect metabolic health and generate obesity. In the meantime, clinical studies applying the principles of circadian resonance to the treatment of human obesity must proceed; their success would most strongly support a causative association between desynchrony and metabolic dysfunction. Medical science has no other effective, non-invasive intervention to offer, and our increasing obese population have nothing to lose but their waistlines.”