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How to reset your internal body clock and get some sleep

Light exposure and meal time may be the key to resetting the "master clock” in the brain.
Image: A man sleeps in bed
Our biological clock, which tells us when to go to bed and awaken, is very sensitive to light.Hero Images / Getty Images/Hero Images

In casual conversation, the “biological clock” is often referred to when starting a family but officially, our biological clocks, or our circadian rhythms, are how our bodies know when to go to sleep at night and when to wake up in the morning. With a few notable exceptions (hospital staff comes to mind, as does the populous of those in far Nordic countries), most of us live lives in which we work at day and sleep at night, loosely following the rise and setting of the sun. However, as any insomniac can tell you, it’s also super easy for our circadian rhythms to go off-kilter.

When they are off, is it possible to reboot our biological clocks? And if so, how should we go about doing it?

Though one McGill University study found a form of steroids might do the trick, a more recent study proves a weekend in the wild might work just as well, if not better. Scientists discovered that the human melatonin rhythm (melatonin is a hormone that helps control your sleep/wake cycles) adapts to short summer and long winter nights when living in a natural light-dark cycle — something that was long assumed but never officially proven.

“Our master brain clock (or biological clock), which tells us when to go to bed and awaken, when to eat and when to be active, is very sensitive to light,” explains Kenneth P. Wright Jr., Ph.D., professor, Department of Integrative Physiology, Director of Sleep and Chronobiology Laboratory at the University of Colorado Boulder, and co-author of the study. “Morning exposure to light and increased exposure to sunlight shifts the master clock earlier.”

Morning exposure to light and increased exposure to sunlight shifts the master clock earlier.

This is why exposure to artificial light, be it in the form of fluorescent office lighting or blue light screens, can throw such a monkey wrench in our sleep cycles, which can negatively impact our health in many unexpected ways. “Almost every tissue in our body has a circadian clock and we now recognize that disturbances in circadian timing and in internal circadian clocks can contribute to major health problems such as obesity, diabetes, heart disease, mood disorders, cancer and cognitive impairment,” says Wright.

Some common circadian rhythm disruptors:

  • Exposure to artificial light at night
  • Drinking caffeine in the evening
  • Jet lag
  • Shift work
  • Eating at night

Though last on Wright’s list of circadian rhythm disruptors, food — or, rather meal timing — has also proven to play a major part in regulating sleep/wake cycles, according to a UK study that set out to establish how circadian rhythms, metabolism and nutrition are linked. Ten healthy men were monitored after eating three meals a day at the same time, then again when their meal times were made a half hour earlier, and again when moved to five hours later than the originally established time for six days. The outcome? The timing of meals really does play a role in synchronizing circadian rhythms.

The timing of meals really does play a role in synchronizing circadian rhythms.

Of these findings, one of the study’s researchers, Jonathan Johnston, reader in chronobiology and integrative physiology with the Faculty of Health and Medical Science at the University of Surrey, says meal times might help ensure our body’s many clocks sync up the way they’re supposed to — though he’s not sure exactly how it all works yet.

“In reality, there may well be multiple biological signals that together synchronize clocks to meal time,” he explains. “Animal studies have shown that clocks outside of the brain (especially in tissues key to metabolism, such as the liver) will synchronize to timed food in preference to other external cues, such as light. How this works is still not clear. There is evidence that glucose (blood sugar) itself can synchronize clocks in cells grown in a dish. I imagine that future studies will explore whether certain types of food are most effective at resetting clocks,” says Johnston.

After all, what you eat and when you eat it can make all the difference in how you metabolize food. “The body processes meals differently at different times of day. For example, it has been shown that blood sugar (glucose) and fat response to a meal varies across the body’s daily cycle,” says Johnston. “In the long term, eating a higher percentage of daily calories in the morning helps weight loss and a higher percentage of calories in the evening leads to weight gain,” he explains. So, in a way, it makes sense that eating a big meal late could potentially keep your body too busy digesting your food to wind down.

Though he says timed light exposure is still the best way of resetting your biological clock, what he refers to as the “master clock” in the brain, Johnston says timed melatonin supplements and timed meals may also help us to speed up acclimation to a new time zone, for example. So, to beat jet lag, absorb as much natural light as you can when you get to where you’re going, dim the hotel lights when you want to settle in and avoid eating dinner too late. And by all means, skip the midnight snack.


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