It is often said that it is an “evil of the century”. A sedentary lifestyle – and physical inactivity – has become a major public health problem. According to the National Observatory of Physical Activities and Sedentary Life (Onaps), we are sedentary for more than seven hours spent sitting or lying awake in a day. What are the effects of this sedentary lifestyle on health? How can we incorporate more activity and movement into our day? Responses from Professor François Carré, cardiologist and sports doctor at Rennes University Hospital, and president of the “Pour une France en forme” collective.
Why Doctor: Why is it so important to fight against a sedentary lifestyle?
Professor François Carré: In recent decades, we have realized that lack of physical activity is not the only problem. Countries like Canada have managed to increase the physical activity levels of its nationals, but there has been no effect on overweight and obesity. For what ? Because we have forgotten to take into account the time spent sitting, which is increasingly important today: in France, an adult sits 12 hours a day when they work and 9 when they do not work; a 7 year old child spends 50% of his day sitting, a 14 year old 75%. However, this sedentary lifestyle represents a real risk for health, since the more time we spend sitting, the more we increase the level of inflammation and oxidative stress in the body. This gives rise to most chronic diseases: diabetes, obesity, cardiovascular diseases, depression, sleep disorders… Today, children even develop “old people’s diseases”, such as type 2 diabetes, which formerly mainly affected men aged 50. In France, between 40,000 and 50,000 deaths per year are linked to chronic diseases caused by physical inactivity.
This sedentary lifestyle also has an impact on our physical capacity, which is our health capital. Basically, the more floors you climb in five minutes, the better your health. But there is only one way to increase this physical capacity, and that is to move. No medication will do it for you.
Our body cannot tolerate a sedentary lifestyle, because it is genetically programmed to move: if we are not moving, we cannot stay healthy.
What happens at the physiological, biological level when we stop moving?
It took humans millions of years to go from four legs to two, and within a few decades we moved to sitting all day. Our body cannot tolerate it, because it is genetically programmed to move: if we are not moving, we cannot stay healthy. We owe it to our ancestor Homo sapiens, who bequeathed us his endurance genes in particular: when they are activated, these genes release proteins which will reduce inflammation, oxidative stress, etc. But to get these genes started, you have to move, otherwise they stay in the genome and are of no use. We often say that “it’s good to move and do physical activity”, but we should above all say that “it’s very dangerous not to do it”.
Why are the numbers of sedentary lifestyles increasing? Is it the fault of screens, working conditions, increasingly indoor and seated leisure activities?
All this, and screens, of course, have made us even more sedentary. The youngest are particularly affected: we recently learned that in the United Kingdom, children spend less time outside during the week than prisoners. In France, they spend less than 15 minutes outside per day, on average per week, and they spend more time sitting during the holidays than during school. They also say they are increasingly depressed. However, we know that the first treatment for depression is physical activity: by moving more, they would feel better, mechanically. We’re not even talking about doing sports, just physical activity, 30 minutes a day for adults and 1 hour for children. But it’s difficult to get the message across because people don’t believe that a sedentary lifestyle is as harmful as junk food. Worse, they feel like it’s the norm, since the overwhelming majority are too sedentary or overweight. How to question yourself? In the United States, 90% of the population is overweight, so it’s “normal” to be overweight. In France, we are 46% adults, and the obesity rate among 18-24 year olds has quadrupled since 1993.
Like all addictions, the chair kills. And silently, because we don’t realize that we are developing an illness
You say that “the chair does not rest on us”on the contrary. The more we sit, the less our body moves and the more tired it is – and vice versa?
I talk about the chair as an addiction: we sit systematically, without even realizing it, even though we don’t need it, and we keep coming back to it more and more. Like all addictions, the chair kills. And silently, because we don’t realize that we are developing an illness: there are no symptoms when we are diabetic, when we are hypertensive, or when we have cancer until it sneaks up. . Moreover, you can very well be thin and in poor health because you are too sedentary, just as you can be very overweight and have a very good cardiorespiratory condition.
And the chair lies, because it makes us believe that it is resting us. When you come home from a tiring day, collapsing on the couch is not going to give you any more rest or relieve your leg pain. But if you go for a five or ten minute walk, you will have less pain – this has been formally demonstrated. If we say we’re so “tired”, it’s simply because we’ve lost the habit of moving! Let’s look at our travel: even for distances of less than 2 km, the car remains the main mode of transport today, at more than 50%.
Should we ban sitting as soon as possible?
Above all, we must adopt what we call “sedentary lifestyle while moving”. In the office, you can sit while being active, for example by installing a small pedal board under your feet. Even five minutes every hour has shown benefits on blood pressure, cholesterol, etc. The important thing is to break periods of sedentary lifestyle, the worst being periods of more than 1h30 without moving: every hour or more, get up, go see a colleague, look out the window… When you stay sitting too long, our body goes into hibernation, it becomes clogged. We feel cold because our body temperature drops, like when we fall asleep. Same thing for the brain: by sitting for too long, it becomes less vigilant because it is no longer perfused. Just get up for a few minutes to revive it and refocus.
There are solutions. So-called “standing” desks are no less bad for cardiovascular health, but they relieve back problems. Because we must not forget that we often sit in a bad position: the more time passes, the more we slouch. This causes what we call gluteal amnesia: the muscles of the buttocks are those which keep the back straight, but when you sit for 4 hours, they have not worked, and when you get up, they do not start. in action. It is therefore the muscles along the vertebrae which take over, except that this is not their role, so it hurts. The advantage of the Swiss Ball is that your glutes are constantly working.
Between 1987 and 2022, the physical capacity of 11-year-old children increased from 11.2 to 9.7 km/h over 1 km of running. The good news is that we can reverse the curves.
In 2022, you led a study on the decline in physical capacity of children, who run slower than 30 years ago…
The work was carried out on nearly 10,000 11-year-old middle school students in three regions: between 1987 and 2022, their physical capacity increased from 11.2 to 9.7 km/h (on average over 1 km of running). In other words, an 11-year-old child can’t keep up with an active 60-year-old man for a mile. If we extrapolate a little, the health capital of an 11-year-old child would today be equal to the health capital of a sixty-year-old… The good news is that we can reverse the curves: ten sessions of interval running for six weeks (as part of classic PE classes) made it possible to reduce this drop in their physical capacity by 44%. It’s never too late: by deciding to move, even at 80, you improve your health. The benefits of movement and physical activity – a therapy in its own right validated by the High Authority for Health (HAS), let us remember – are seen even in patients. A surgeon I know, specializing in digestive cancers in the elderly, recently suggested that her patients walk 15 minutes every day during the two or three weeks before their operation. As a result, she found that those who follow her walking prescriptions leave three days after surgery, compared to six days for those who did not walk.
Can we “cancel” the consequences of a sedentary lifestyle by integrating physical activity into our day?
To compensate for 10 hours of sitting per day, you need to practice around 2 hours of physical activity… Unfortunately, those who sit 12 hours per day are those who practice the least. Above all, you must keep in mind that it is by moving every day – by climbing the stairs, by cooking, by doing crafts, by walking your dog, etc. – that you take care of your health. Every minute less spent sitting, every step more, is beneficial for the body. Be active first, then you will see if you want to take up sport more seriously.
