How Much Sitting Is Too Much?

Among the many reasons I love my dog, Echo, is that she helps expose my hypocrisies. When not chasing squirrels, barking at the mailman, or ­going for walks, Echo is a lazy creature who spends untold hours reposing. She sometimes sleeps on the hard floor, but she prefers to relax on carpets, couches, upholstered chairs, and any other warm, soft place she can find. When I tease her about her slothful ways, she gazes back wordlessly, and I know what she is thinking: “How are you any different from me?”

Yes, I too travel about the house sitting in various comfy, pleasant spots, and much as I try to stand more often, I am no less of a compulsive sitter than Echo.

And for good reason: Sitting is less tiring and more stable than standing. Studies that compare the energy spent standing with that spent sitting report that standing costs about 8 to 10 percent more calories than sitting quietly in a simple desk chair. For a 175-pound adult, this difference is a modest eight calories per hour — the ­number of calories in an apple slice. Over time, these calories could add up: a typical white-collar worker who stands rather than sits on the job potentially burns an extra 16,000 calories a year. In case it makes you feel better, bipedal humans apparently stand more efficiently than bipedal birds or large four-legged animals like cows and moose (yes, someone measured how much energy moose spend standing). Humans also stand more efficiently than apes because we can straighten our hips and knees, and our lower spine has a backward curve that positions our torsos mostly above rather than in front of our hips. Even so, muscles in our feet, ankles, hips, and trunk must work intermittently when we stand to prevent us from swaying too much or toppling over.

Regardless of how efficiently we stand, the benefits of conserving a few calories per hour by sitting accrue so much over time that the instinct to sit is no less a universal habit among humans than among other animals like Echo. Further, like other creatures, humans until recently sat without chairs. Hunter-gatherers rarely make furniture, and in many parts of the non-Western world, people still sit often on the ground. In a delightfully comprehensive study, the anthropologist Gordon Hewes documented more than a hundred postures that humans from 480 different cultures adopt when they sit without a chair. Chairless humans often sit on the ground with their legs stretched out, cross-legged, or to the side; sometimes they kneel on one or two legs; and frequently they squat with their knees so bent that their heels either touch or come close to the backs of their thighs. If you are like me, you rarely squat, but that avoidance is a modern Western peculiarity. Because squatting creates tiny smoothed regions on ankle bones known as squatting facets, we can see that humans for millions of years, including Homo erectus and Neanderthals, regularly squatted.

My lack of stamina while squatting highlights how addicted I am to chairs, especially those with backrests. Whenever I sit on the ground or use a stool without a backrest, muscles in my back and abdomen must do a little work to hold up my torso, and when I squat, muscles in my legs, especially my calves, are also sometimes active. To be sure, the muscular effort isn’t great: Squatting and standing use about the same degree of muscle activity. But over long periods of time those muscles require and develop endurance. Studies show that backrests demand less sustained muscular effort. It is reasonable to conclude that those of us who regularly sit in chairs with backrests have weak back muscles that lack endurance, making it uncomfortable to sit for long on the ground or on stools. The result is a vicious cycle of chair dependency.

A reliance on chairs with backrests is unquestionably recent. Archaeological and historical evidence suggests that in most cultures, chairs with backs, wherever they first appear, were used primarily by high-ranking person­ages, while peasants, slaves, and other laborers mostly had to sit on stools and benches. In Europe, it was not until the late 16th century that chairs with supportive backs started to become common among the growing middle and upper classes who could afford ­furniture. Then, ­during the Industrial Revolution, a German manufacturer, Michael Thonet, figured out how to mass manufacture bentwood chairs with backrests that were light, strong, beautiful, comfortable, and affordable to the needy masses. Today, billions of people have no choice but to sit much of the day, and then after an exhausting day of sitting, they follow deep-seated instincts to save a few more calories by sitting at home to relax. But for how long do we really sit on any given day?

Many studies use self-reported estimates, but we tend to be inaccurate, biased judges of our activities, sometimes claiming activity levels as much as four times higher than reality. Today scientists can easily collect more objective and reliable data using wearable sensors that measure heart rate, steps, and other movements. Curious, I decided to measure how much I actually sit by wearing a tiny accelerometer. These thumb-sized devices record how forcefully a body is moving in different directions every second over the course of days or weeks. They record minimal accelerations if one is sedentary, moderate accelerations during walking, and high accelerations during vigorous activities like running. For a week I clipped one to my waist from the moment I woke up to the time I went to bed. I then downloaded the data to quantify how much time I spent sitting or moving at light, moderate, and ­vigorous levels.

The results of my week of self-measurement surprised me. First, I was less sedentary than I expected. On average, I spent 53 percent of my wakeful hours sitting or otherwise immobile. My sitting time, however, varied ­enormously from day to day. My average was 8 ½ hours. My percentage of sedentary activity, it turns out, isn’t much different from that of many Americans. High-­quality studies that measured thousands of people find that average adult Americans are sedentary 55 to 75 percent of the time they are awake. Given that most Americans are in bed about seven hours a night, the average time spent being effectively immobile adds up to between 9 and 13 hours a day.

We are more sedentary than earlier generations. There is evidence that the total time Americans spent sitting increased 43 percent between 1965 and 2009, and there are three major, related health concerns about long periods of uninterrupted sitting. The first is what we are otherwise not doing. Every hour spent resting comfortably in a chair is an hour not spent exercising or actively doing things. The second concern is that long periods of uninterrupted inactivity harmfully elevate levels of sugar and fat in the bloodstream. Third and most alarmingly, hours of sitting may trigger our immune systems to attack our bodies through a process known as inflammation.

The mechanisms by which too much fat, especially in and around organs, can ignite low-grade, chronic inflammation suggest that too much sitting may be hazardous simply because it causes weight gain. It bears repeating that sitting in a comfy chair barely taxes one’s muscles. In contrast, even squatting or kneeling requires some ­muscular effort, and just standing burns about 8 more calories per hour, and light activities like folding laundry can expend as much as 100 calories per hour more than sitting. These calories add up. By merely engaging in low-intensity, “non-exercise” physical activities for five hours a day, I could spend as much energy as if I ran for an hour. So if I sit instead of move, the calories I consumed at lunch are more likely to be converted to fat rather than burned.

A second way lengthy periods of sitting may incite widespread, low-grade inflammation is by slowing the rate we take up fats and sugars from the bloodstream. When was the last time you had a meal? If it was within the last four or so hours, you are in a postprandial state, which means your body is still digesting that food and transporting its constituent fats and sugars into your blood. Whatever fat and sugar you don’t use now will eventually get stored as fat, but if you are moving, even moderately, your body’s cells burn these fuels more rapidly. Put simply, regular movement, including getting up every once in a while, helps prevent chronic inflammation by keeping down postprandial levels of fat and sugar.

Another worrisome way sitting can provoke inflammation is through psychosocial stress. Sadly, sitting is not always relaxing. Long hours of commuting, a demanding desk job, being sick or disabled, or otherwise being confined to a chair can be stressful situations that elevate the hormone cortisol. This much-misunderstood hormone doesn’t cause stress but instead is produced when we are stressed, and it evolved to help us cope with threatening situations by making energy available. Cortisol shunts sugar and fats into the bloodstream, it makes us crave sugar-rich and fat-rich foods, and it directs us to store organ fat rather than subcutaneous fat. Short bursts of cortisol are natural and normal, but chronic low levels of cortisol are damaging because they promote obesity and chronic inflammation. Consequently, long hours of stressful sitting while commuting or at a high-pressure office job can be a double whammy.

Last, and perhaps most important, prolonged sitting can kindle chronic inflammation by allowing muscles to remain persistently inactive. Without going into too many details, we have learned that even modest levels of physical activity dampen levels of chronic inflammation, including in obese people.

The discovery that using your muscles inhibits inflammation provides yet another compelling explanation for why endless hours of sitting are associated with many chronic diseases. By remaining inert for hour upon hour, our bodies never extinguish that faint inflammatory fire that may otherwise be smoldering in the background. In fact, none of the mechanisms that inflame us — swollen fat cells, too much fat and sugar in the bloodstream, stress, and inactive muscles — are caused by sitting per se. Instead, they result from the absence of being sufficiently physically active, which usually means a lot of sitting. Given that sitting for hours a day is an utterly normal behavior both in the past and today, are there better, less inflammatory ways to sit?

Short bouts of activity wake up our muscles and thus keep down levels of blood sugar and fat. When we squat, periodically stand, or do light activities like pick up a child or sweep the floor, we contract muscles throughout the body. Like turning on a car engine without driving anywhere, these light activities stimulate muscle cells to consume energy, turn on and off genes, and perform other functions. It bears repeating that washing the dishes or doing other light chores can burn as much as 100 additional calories per hour beyond just sitting. These activities aren’t serious exercise, but experiments that ask people to interrupt long periods of sitting even briefly — for example, just 100 seconds every half hour — result in lower levels of sugar, fat, and so-called bad cholesterol in their blood. In turn, less circulating blood sugar and fat prevent inflammation as well as obesity. Sitting for long hours without moving increases the risk of swelling (edema) and developing clots in veins. For this reason, squatting and other more active forms of sitting may be healthier than sitting in chairs by requiring intermittent muscle activity, especially in the calves, thus recirculating blood in the legs.

Another way to sit actively is to fidget, or do what researchers drily term “spontaneous physical activity.” In one study, individuals who fidgeted spent between 100 and 800 calories more per day than those who sat inertly. Other studies have found that simply fidgeting while seated can expend as much as 20 calories an hour as well as promote beneficial levels of blood flow to restless arms and legs.

Among the many hyperbolic statements written about sitting, maybe the most extreme is that sitting is the new smoking. While cigarettes are novel, addictive, expensive, smelly, toxic, and the world’s number one killer, sitting is as old as the hills and utterly natural. More truthfully, the problem isn’t sitting itself, but hours upon hours of inactive sitting combined with little to no exercise. If our ancestors from generations ago behaved like today’s hunter-gatherers and farmers, then they likely sat for 5 to 10 hours a day, as much as some but not all contemporary Americans and Europeans. But they also got plenty of physical activity when not sitting, and when these chairless ancestors plunked themselves down, they didn’t rest in supportive chairs with seat backs; instead, they squirmed as they squatted, kneeled, or sat on the ground, using about the same degree of muscle activity in their thighs, calves, and backs as when they stood.

Because desk jobs are here to stay for the foreseeable future, standing desks have been widely advertised as a panacea for excess sedentariness. Such marketing deceptively confuses not sitting with physical activity. Standing is not exercise, and as yet no well-designed, careful study has shown that standing desks confer substantial health benefits.

And while we are at it, other exaggerated statements about sitting may also be myths. How often have you been admonished to stop slouching and sit up straight? This old chestnut dates back to the late-19th-century German orthopedic surgeon Franz Staffel. As the Industrial Revolution caused more people to work long hours in chairs, Staffel worried these sitters were ruining their posture by sliding their buttocks forward and straightening their lower backs. Alarmed, Staffel opined that a person’s spine should maintain the same characteristic double-S curve when sitting as when standing normally, and he advocated chairs with lower back supports to force us to sit upright. Decades later, Staffel’s opinions were backed up by the Swedish ergonomics pioneer Bengt Åkerblom and his students, who x-rayed people in chairs while measuring their muscle activity. As a result, most Westerners, including a majority of healthcare professionals, think we can avoid back pain by sitting with a curved lower back and an unrounded upper back. Scientific evidence discredits this modern cultural norm: Nearly all high-­quality studies on this topic fail to find consistent evidence linking habitual sitting in flexed or slouched ­postures with back pain. I was also surprised to read there is no good evidence that people who sit longer are more likely to have back pain, or that we can lessen the incidence of back pain by using special chairs or getting up frequently. Instead, the best predictor of avoiding back pain is having a strong lower back with muscles that are more resistant to fatigue; in turn, people with strong, fatigue-resistant backs are more likely to have better posture. In other words, we’ve confused cause and effect.

So if you are feeling guilty or concerned because you are sitting now, perhaps slouching, keep in mind that you evolved to sit just as much as you evolved to be active. Instead of vilifying chairs and remonstrating yourself for slouching or not squatting, try to find ways to sit more actively without being inert for too long, squirm shamelessly, and don’t let sitting get in the way of also exercising or otherwise being physically active.

Daniel E. Lieberman is the Edwin M. Lerner Professor of Biological Sciences and professor of human evolutionary biology at Harvard University and author of The Story of the Human Body: Evolution, Health, and Disease.

From EXERCISED: Why Something We Never Evolved to Do Is Healthy and Rewarding by Daniel E. Lieberman, published by Pantheon Books, an imprint of The Knopf Doubleday Publishing Group, a division of Penguin Random House LLC. Copyright © 2020 by Daniel E. Lieberman. EXERCISED will be available as a paperback from Vintage books in December.

This article is featured in the January/February 2022 issue of The Saturday Evening Post. Subscribe to the magazine for more art, inspiring stories, fiction, humor, and features from our archives.

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