If You Only Take One Daily Walk, Make Sure It's In The Morning — Here's Why
"I always go out before it is quite light," wrote the author Harriet Martineau in 1847. "These early walks are good, among other things, in preparing me in mind for my work." Martineau didn't need science to convince her of the panoply of benefits acquired on an early-morning stroll. Today, those benefits—those "other things"—have been confirmed: if you take just one daily walk, do it first thing in the morning.
The benefits of taking a morning walk.
Why? Because light is the primary timekeeper1 for every cell in our body. And if we get an injection of light within an hour of waking, each cell and neuron can set itself accordingly. We don't need hours of light—a 10-minute walk is enough. Nor should we be deterred by poor weather because even dim and cloudy daylight contains many more lux (the measurement used for light intensity or brightness) than indoor lighting can provide.
Optimizes the circadian rhythm
Our light sensitivity is at its lowest when we first wake up, meaning we need a bright blast to alert our brain and to set our circadian rhythms for the day. Numerous studies have shown that how we spend the first hour of waking can make or break our chances of a good night's sleep. Morning light tells the layer of neurons behind our eyes that it's time to get going, ensuring that our production of melatonin (the hormone that makes us feel drowsy and helps us sleep at night) eases off. But a shock of morning light also sends cortisol flooding through our bodies—waking us up, energizing and invigorating us. Ideally, a few minutes of our morning walk should be without sunglasses, unless it's a dazzlingly bright day.
Morning light also triggers our bodies to make serotonin, a chemical produced by our nerve cells that makes us feel good. Serotonin regulates how well we sleep, later converting to the very melatonin we need to sleep soundly2. Odd though it seems, an early-morning walk might be the very best thing we can do to improve our nighttime sleep.
Supports cardiovascular health
Morning light has the potential to do far more than wake us up and help us sleep. An early-morning walk could also protect our hearts: A recent study suggests that bright light can protect and enhance our cardiovascular health3 by boosting a specific gene that strengthens blood vessels and cuts our risk of a heart attack. Scientists had already spotted a link between light and heart disease, noting the greater prevalence of heart attacks during winter months. But this study revealed something intriguing: Participants exposed to 30 minutes of intense light between 8:30 and 9 a.m. for five consecutive days had raised levels of a protein called PER2. PER2 is critical for setting circadian rhythms, improving metabolism, and fortifying blood vessels. Earlier versions of the same experiment on blind mice found bright light had no effect, hinting at the crucial role our eyes play.
In these experiments, the intense light measured 10,000 lumens. To put this in context, European daylight ranges from 1,000 to 100,000 lumens depending on the time of day and year, latitude and location, and how overcast the sky is. A typical semi-cloudy British morning in winter might reach a peak light intensity of 16,000 lumens. In summer this rises to around 70,000 lumens. No indoor gym can compete (average indoor lumens is closer to 500). Nor can walking beside a window because glass filters out some of the UV light that also helps set our biological clock.
Promotes metabolic health
It's not only our circadian rhythms that benefit from an early-morning walk. A 2012 study found that women who took a brisk 45-minute walk at 8 a.m. every day were more active for the rest of the day. They were also less responsive to pictures of food. This was one of the first reports to establish that exercise energizes us while simultaneously—and a little perversely—suppressing our appetite. Some researchers now think we eat less after exercise because brisk movement raises our body temperature, activating hypothalamic neurons, which help us control food intake. Just as we eat less when it's warm outside, so we eat less when our bodies are warmed by walking.
But a newer theory posits that we eat less after being active because of a hormone called growth differentiation factor 15 (GDF-15), which our bodies produce when we move (two hours of movement can cause our levels of GDF-15 to swell fivefold). Researchers know that GDF-15 suppresses appetite in rodents and monkeys and are now investigating its effects on human beings4. Either way—heat or hormone—an early-morning walk may well curb excessive feelings of hunger, helping us regulate and moderate our appetite.
After 14 years of walking dogs and children every morning, I found myself addicted to a start-of-the-day romp. Now, like Martineau, I appreciate the opportunity to collect myself, to plan my day: The health benefits are a serendipitous byproduct.
From 52 WAYS TO WALK by Annabel Streets, published by G.P. Putnam's Sons, an imprint of Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2022 by Annabel Streets.
Annabel Streets is a writer of highly researched, award-winning fiction as well as both narrative and practical nonfiction. She is the author, writing as Annabel Abbs, of the forthcoming nonfiction book Windswept: Women Who Walked (Tin House, September 2021), a feminist meditation on the power of walking in the lives of several extraordinary women, including Georgia O’Keeffe, Simone de Beauvoir, and Frieda Lawrence. Under the name Annabel Streets, which she uses for her practical nonfiction, she is coauthor of The Age Well Project (Piatkus, May 2019). She is the author the novels The Joyce Girl (William Morrow, June 2020), the story of James Joyce’s daughter Lucia, and of the forthcoming Miss Eliza’s English Kitchen (William Morrow, September 2021), which has been described as a Julie & Julia set in Victorian England.