Sitting for hours is risky
Risk of diseases from hours of inactivity
The inactive are most at risk
Any movement is good
Exercise does not have to be strenuous
Risk of diseases from hours of inactivity
If you sit for hours every day, you are at serious risk of heart and vascular disease, some cancers, obesity, kidney problems, dementia, diabetes, metabolic syndrome and several other degenerative diseases. (2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20)
These risks remain elevated even if you exercise but then spend the rest of the day inactive in a chair. (12, 14)
Unfortunately, most of us sit for long periods every day:
- In front of a computer, working, socialising or playing games.
- Watching TV.
An Australian study (5) of more than 222,000 people aged 45 or over found that those who sat for 11 or more hours a day had a 40% increase in the risk of dying over the next three years, compared with those who sat for only four hours a day. These results allowed for how healthy they were, their levels of physical activity and their weight.
Another meta-study combined the results of 18 other studies of nearly 800,000 people. (6) The lead researcher Emma Wilmot, said it was clear that those who sat the most had a substantially higher risk of diabetes, heart disease and death than those who sat the least.
Both these studies confirmed that long periods of sitting are damaging to your health, and increase these risks EVEN if you do 30 minutes of exercise per day. (5) Long periods of sitting and inactivity need to be broken up with movement.
The inactive are most at risk
A large study (8) published in 2015 found that the sickest people and those at the most risk of death are those who do no exercise whatsoever (those who are classed as inactive). The researchers found that when inactive people performed even small increases in activity there were big benefits.
The greatest reductions in the risk of premature death were seen when those who were completely inactive became moderately active.
This study also found that lack of exercise is twice as likely to kill you as obesity.
All it takes to avoid dying prematurely is a brisk 20 minute walk each day. People who engaged in moderate levels of exercise such as taking an energetic 20 minute daily walk - were 16% to 30% less likely to die than the inactive.
A 2015 study of 5,700 elderly men in Norway showed that those doing three or more hours of exercise per week lived five years longer than the sedentary. (9)
Even a few minutes of walking and moving around each hour instead of remaining sitting can substantially reduce the harm from inactivity, according to a 2015 study of chronic kidney disease. (10)
Scientists examined the effects of obesity and exercise on 334,161 European men and women over a period of 12 years. The participants had an average age of around 50. Just under a quarter (22.7%) were categorised as inactive, working in sedentary jobs without doing any recreational exercise.
Study leader Professor Ulf Ekelund, from the Medical Research Council (MRC) Epidemiology Unit at Cambridge University, said: "This is a simple message: just a small amount of physical activity each day could have substantial health benefits for people who are physically inactive... Although we found that just 20 minutes would make a difference, we should really be looking to do more than this - physical activity has many proven health benefits and should be an important part of our daily life."
Any movement is good
The good news is that lots of research (1, 12, 16, 17, 18, 19, 20) shows that regular, short, and quite gentle exercise breaks can make a big difference to the dangers of sitting for long periods.
David Dunstan said: "As recently as two decades ago, people were moving more frequently throughout the day in the workplace. Prior to email, people had to collect mail from a pigeon hole, or walk over to people's desks for a chat. I think we've reached a crisis point where we need to step back and acknowledge that sitting for long periods is not what our bodies were designed for."
"When we sit, we have muscle 'dis-use' - our muscles are essentially 'sleeping'. When we're up and moving, we're contracting muscles and it appears that these frequent contractions throughout the day are beneficial for helping to regulate the body's metabolic processes."
"When we eat, we get rises in blood glucose. With larger and more frequent rises in blood glucose, we gradually accumulate damage to the walls of our veins and arteries. This increases our susceptibility to heart disease."
One of the keys to good health and a long life is a low, steady level of glucose and insulin in your blood. Repeated spikes, or continuing high levels of blood glucose rapidly age your body and contribute to numerous degenerative diseases (heart and arterial disease, diabetes, cancers). Insulin, and how effective it is, is the main factor controlling blood sugar levels.
The study (1) looked at subjects aged 45-65 who were overweight or obese, with a body mass index (BMI) above 31. Each of them did three different five hour sits. In the first, they sat for 5 hours without a break. In the second, they walked on a treadmill at a light-intensity pace for 2 minutes every 20 minutes. In the third, they walked on a treadmill at moderate-intensity pace for 2 minutes every 20 minutes.
The researchers found that the participants' blood glucose and insulin levels after consuming a high-calorie meal were moderated when they performed regular two minute bouts of either light or moderate-intensity activity.
Dunstan again: "In a controlled laboratory environment that mimicked the typical patterns of desk-bound office workers, participants who interrupted their sitting time with regular activity breaks, showed up to 30 per cent improvement in the body's response to a meal containing glucose. The good news is that the improvements were seen even with light-intensity activity, which is the equivalent of strolling."
The participants in the study were all overweight, and it showed that even light exercise has substantial benefits for them. But Dunstan emphasised that the findings are not confined to people who are overweight and suggest that everyone can benefit from breaking up their sitting time.
Another study found that every hour that overweight adults spent watching television (a good proxy for inactivity) increased their risk of becoming diabetic by 3.4%. Most of the study's participants were watching nearly three hours a day. (13)
A massive study (16) of 130,000 people in 17 countries was published in the prestigious journal The Lancet in 2017. It confirmed that gardening, housework, and indeed any activity for 30 minutes a day reduces your risk of death from any cause by 28%, while heart disease was reduced by 20%. It did not matter what kind of activity the subjects did. With more activity, the benefits were even better. For example, those walking briskly for 750 minutes per week had a 36% reduction in risk of death.
Exercise does not have to be strenuous
The researchers found that the benefits of walking at a light intensity pace were almost identical to walking at a moderate intensity pace. This suggests that it is not so much the amount of effort put into the exercise break that was critical, but simply that the act of regularly standing up and moving around is highly beneficial.
This means that you don't need to pant and puff and work up a sweat. Just standing up, walking around, using the stairs instead of the elevator and standing while on the phone or at a meeting are all likely to help.
If you watch TV, get up during the commercial breaks, do some housework, walk around (advertising breaks are a blessing in disguise). Take a walk during your lunch break. Conduct one-on-one meetings while walking outdoors with colleagues.
Long periods spent sitting, independent of other physical activity, are quite harmful. Just sitting, with a lack of physical activity, can raise blood triglyceride level, blood sugar, blood pressure, C-reactive protein (CRP) (3), and stimulate the appetite hormone leptin. These are risk factors for obesity, cardiovascular disease, inflammation mainly in women (3), rapid aging, and several other chronic degenerative diseases.
A study published in 2017 (15) found that the benefits from running (and other exercises) are about the same no matter how much or little you run. Those who run for 150 minutes or more a week or ran the fastest lived longer than those who did not run. However, the intense runners did not live significantly longer those who ran the least, including people running as little as 5 to 10 minutes a day at a leisurely pace of 10 minutes a mile or slower.
A new field that some researchers refer to as "inactivity studies" looks at why people on measured, identical diets can have very different body weights. A major finding is that people who stay slim keep moving. They have the natural habit of moving around in small unconscious ways, whereas those who gain weight just sit still.
James Jensen, referring to his research (4) says "The people who didn't gain weight were unconsciously moving around more. They hadn't started exercising more - that was prohibited by the study. Their bodies simply responded naturally by making more little movements than they had before the overfeeding began, like taking the stairs, trotting down the hall to the office water cooler, bustling about with chores at home or simply fidgeting. On average, the subjects who gained weight sat two hours more per day than those who hadn't."
These inactivity studies confirm that sitting still for extended periods is closeley associated with metabolic syndrome, diabetes, cognitive decline and several forms of dementia, cardiovascular diseases, inflammation in various forms, several other degenerative diseases, and of course, obesity.
A 2015 study of overweight adults found that for each hour they sat watching TV (a good proxy for inactivity) they increased their risk of becoming diabetic by 3.4%. (11)
Breaking up your exercise into small, manageable segments throughout the day is MORE beneficial than the same length of exercise in one continuous bout.
A study (14) published in October 2016 found that a single vigorous workout each day may do little to counter the effects of prolonged sitting. In contrast, strolling around frequently and moving throughout the day in addition to strenuous exercise seems to keep harmful triglycerides under control.
The study had seven healthy young male volunteers wear monitors and spend four active days in a row and four sedentary days in a row. On the active days the men walked as often as they could, averaging more than 17,000 steps while sitting for only eight hours per day. On sedentary days, they sat for about 14 hours.
Lead author Edward F. Coyle said that the active days caused a healthful reduction of triglycerides - fats associated with heart disease that enter the bloodstream after a big fatty meal. However, on inactive days strenuous running did not bring down the high levels of triglycerides in their blood. "So much sitting seems to have made the men's bodies exercise-resistant," Coyle says.
The take home message is that we should walk and move as much and as often as we can.
1. Dunstan, David et al.
Significant health benefits for overweight adults in breaking up prolonged sitting.
Baker IDI Heart and Diabetes Institute, published online 29 February 2012 in Diabetes Care -
a publication of the American Diabetes Association.
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