The average person sits from five to six hours per day. This isn’t surprising given most people have a job that demands sitting. While there’s no guideline on how little one should sit, it’s recommended adults reduce time in sedentary behaviours and get at least 30 minutes of moderate or vigorous activity on most days. But is that enough activity to counteract your sitting?
What happens to your body when you sit?
The human body is an efficient machine. It revs up your metabolism when you’re moving and it slows it down when you’re not. Just like new cars that shut off their engine at stop lights, your body does the same when you sit. For a 150-pound person, sitting requires about 68 calories per hour. Most of these calories are needed just to keep your body functioning. And standing only burns another 10%-20% more. In contrast, a brisk walk will require nearly 300 calories for that same hour.
As a result of the reduced metabolic needs, your body slows down. Enzymes (proteins that are needed for chemical reactions) that break down fats and sugars in the blood shut down. This leaves the fats and sugars to circulate in your blood stream. While you need a certain amount fats and sugars in the blood, too much can increase your chances of getting diabetes, heart disease, cancer and early death.
In addition, if you sit too long, you might find your muscles and joints getting stiff from lack of movement. Sitting for long periods is also associated with low back pain and can decrease lumbar disc height. And as you sit more, and are less active, you may find your strength and fitness going down as well.
Benefits of Physical Activity
If sitting, and lack of movement, are bad for you, the obvious answer is to move more. For those who are active, the most common pattern is to sit all day and then go out and exercise. Usually on one’s leisure time. While this is good, and better than doing nothing, it may not be enough to counteract all that sitting.
People who are active have a lower risk for diabetes, heart disease, certain cancers and live longer. In many of these studies, comparison is made between those who are active and those who aren’t. Rarely do these studies consider how much sitting, or sedentary time, the participants engage in. It’s generally assumed people who are more active sit less. And to some extent that’s true, but not always.
However, even in people who are active, higher levels of sitting is associated with a shorter lifespan. People who were active for at least an hour per day but sat for more than six hours had a 40% greater risk for early death, compared to people who sat for less than half that. Even people who were much less active, but also sat less had a lower risk. A separate study found that while 30 minutes of exercise was associated with an 80% reduction in chances of early death, this benefit was gone in those who sat for ten or more hours per day.
One reason for this, is that the metabolic effects of prolonged sitting may not be easily countered by a small amount of exercise. Following four days in a row of mostly sitting, a one-hour bout of exercise made no difference in terms of blood sugars and fats compared to those who didn’t exercise.
What is the solution?
Of course more movement would help. But it doesn’t necessarily mean you need to spend more time exercising (although that would be good too). It could just mean spending less time sitting and in other sedentary activities, which can be replaced by light activities. Light activities, or non-exercise activity thermogenesis (NEAT), are at an intensity below a brisk walk. This is the majority of activity many of us do and includes things from standing up, to walking to household chores. If you’re already active for 30 or more minutes per day, replacing sitting time with light activity has a similar benefit than if you replaced it with more intense activity.
It’s also not just how much activity you get. It’s also important as to when you get it. Getting up and walking around for as little as two minutes every 20 minutes has been shown to reduce blood sugars by more than 20% compared to continuous sitting. This is because even that little movement turns your body’s enzymes back on.
You can even increase your activity levels when sitting down. People who fidget burn around 50% more calories than those who don’t. This small amount of movement may be enough to keep your enzymes active, and burning fats and sugars. And people who fidget while sitting tend to live longer than those who don’t.
While regular activity and exercise have numerous benefits, the best way to counteract sitting is to do less sitting and have frequent movement breaks.
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