Daniel LIEBERMAN
In fact, we were born to be lazy, explains Harvard’s evolutionary biology expert, Daniel Lieberman
According to my iphone, my non-exercise step counts have declined by about 50 per cent since the start of the pandemic. I’ll make a bet that is the case for you, too. According to recent studies, Britons working from home spent nearly an extra hour a day at their desks, and rates of sedentary behaviour are rising faster in the UK than in any other European country.
Are you worried that your excess sitting will make you sick, or are you sick of being told you should worry about your sitting? Strange as it may seem, both concerns may be true.
Despite Ogden Nash’s observation that “people who work sitting down get paid more than people who work standing up,” a chorus of experts warn we are sitting too much, and condemn sitting as the new smoking.
One prominent US physician contends that chairs are “out to get us, harm us, kill us” and that “for every hour we sit, two hours of our lives walk away – lost forever”.
Such alarming statistics might goad us to exercise, but can also make us exercised about sitting. Increasing numbers of people are buying standing desks and wearing sensors to keep track of and limit our sitting time.
There is no doubt that too much sitting has the potential to hasten your demise, but are we treating it like so many other topics related to health and disease by oversimplifying, medicalising and pathologising something very normal? Also, what do we do about the fact that it is nearly impossible to avoid it?
I think we can agree that sitting is rather pleasant and comfortable, and doing discretionary physical activity solely for the sake of health and fitness – that is, exercising – may be healthy, but it is also a modern, unnatural behaviour that we never evolved to do.
I am a middle-aged professor of human evolutionary biology at Harvard University, who – true to the cliché – was picked last for sports teams as a child in school. However, I always enjoyed jogging and hiking, and became well-known for my research on how humans evolved to run long distances, which inspired me to become a more serious runner myself. I still run marathons regularly but I have also become increasingly concerned about today’s highly medicalised and commercialised attitudes about exercise. My field research around the world has made me intensely aware that you don’t need to run marathons, get buff or rush out to buy a standing desk to be healthy.
Instead, I think it’s helpful to recognise we inherited deep-seated tendencies to take it easy whenever possible, but to be moderately physically active, especially as we age.
As a first step, let’s ask how much we actually sit. High-quality studies that used sensors to monitor thousands of people find that average American adults are sedentary 55 to 75 per cent of the time they are awake, which translates to between nine and 13 hours a day; UK workers evidently sit about the same amount. Unsurprisingly, we sit more on weekdays, and we sit more as we get older, and, yes, we probably sit more during lockdowns.
That’s a lot of sitting, but what is normal? From an evolutionary perspective, “normal” is what our hunter-gatherer ancestors did before we invented agriculture, not to mention desk jobs, commuting and televisions. I’ve had the privilege to spend time with hunter-gatherers, and although they are considerably more physically active than the average Westerner, they, too, spend much of the rest of their day sitting. My impression was recently backed up by a study of sitting among Hadza hunter-gatherers in remote Tanzania. The sensors these scientists used showed that the
Hadza sat on average about nine hours a day.
Altogether,
Westerners like me spend on average about two hours more sitting than our distant
ancestors.
How much do those extra few hours on our butts affect our vulnerab-ility to getting sick and dying? This relationship, too, is far from straightforward.
Although plenty of scary studies find a correlation between sitting time and mortality rates, other studies report that not all sitting is the same, and it also matters what you are doing when not sitting.
For example, sitting time at home watching television is more strongly associated with bad health outcomes than sitting time at work, presumably because people who watch a lot of television aren’t being physically active after they leave the office. This inference is backed up by massive prospective long-term studies in several countries that have found no association between how much time people spent sitting at work and their risk of illnesses like heart disease. Instead, leisure-time sitting best predicts
mortality rates, suggesting that socioeconomic status and exercise habits have more important health effects than how much one sits during weekdays at the office. Other key variables to consider are how often we interrupt our sitting bouts and the manner in which we sit. Hunter-gatherers like the Hadza rarely sit for more than 15 minutes at a time because they frequently get up to mind children, tend a fire, and do other chores. In addition, they mostly sit on the ground with their legs stretched out, or they squat and kneel, which means they are using some of their muscles at low levels to support their backs and limbs.
Westerners, however, can sit like logs for hours at a time in comfy chairs with backrests without almost any muscular effort. This degree of sitting comfort is novel. Until inexpensive chairs with backrests were first manufactured in the mid-19th century, most people sat on stools, benches or the floor.
Getting up every once in a while and squatting or sitting without a backrest doesn’t consume many calories, but these behaviours use enough energy to lower sugar and fat in the blood, helping prevent the body from becoming chronically inflamed – a major risk factor for chronic illnesses.
Sure enough, people who interrupt their sitting time with frequent short breaks have up to 25 per cent less inflammation than those who rarely rose from their chairs despite sitting the same number of hours.
In addition, a long-term study of 8,000 Americans found much higher death rates among those who tended to sit for half an hour or longer, compared with those who rarely sat for more than 12 minutes at a time.
So, what should we do with this information as we sit at home, sidelined by Covid-19, waiting for a vaccine to permit us to resume our previously mostly sedentary life?
Instead of demonising sitting, why don’t we tell the only slightly more complex truth? That is, sitting for nine or 10 hours a day is neither abnormal nor a death sentence if you are not sitting stock-still for long uninterrupted bouts, and otherwise getting enough physical activity.
There is no one prescription for exercise, but 150 minutes a week is a widely recommended minimum: do mostly cardio but also some weights, remember some is better than none, and keep it up as you age.
Finally, go ahead and binge watch Blue Planet or Peaky Blinders – but as a reward, perhaps, for having first gone for a walk or a jog. Fidget shamelessly, and consider sometimes watching on the floor while stretching. If you must sit glued to your computer, try using a timer to remind you to get up every 1015 minutes. But let’s not falsely equate sitting with smoking.
Exercised by Daniel Lieberman (£25, Allen Lane). Buy now for £22 at books. telegraph.co.uk or call 0844 871 1514.