Man lying on a couch with remote control

Long periods sitting down will slash your life expectancy – even if you exercise every day

Spending long periods sitting down reading a book, at your desk working or in front of the TV, will slash your life expectancy – even if you exercise every day.

So what’s so bad about doing nothing?

Michael Jensen, an exercise researcher at the Mayo Clinic in Rochester, one of the US’s top medical research facilities, was studying weight control when he discovered that some people “on impulse, start moving around and don’t gain weight” when they have eaten too much.

These types of people don’t rush to the gym – they simply walk more, hop up from the settee to run every day jobs or find other reasons to get on to their feet. This got them thinking about the urge to move around and how significant that could be for sustaining good health.

This led them to a field known as “inactivity research”, which is revealing that inactivity, particularly when sitting down, is actually bad for you. They actually discovered that inactivity is bad for you even if you exercise as well.

What this means is, that going to the gym is not a licence to spend the rest of the day on your bum.

In 2010, a team led by Alpa Patel of the American Cancer Society in Atlanta, Georgia, analysed the data from a 14-year study of 123,000 middle-aged adults.

When they compared death rates, between those who spent six hours a day or more sitting down and those who reported three hours or less – and taking into account other factors such as diet – they found something surprising.

Extra time on the couch was associated with a 37% higher mortality rate for women and 17% higher for men. It is not clear why there is such a big gender difference (The American Journal of Epidemiology, vol. 172, p 419).

A further study, by a team at the University of Queensland, Brisbane, analysed data on the TV viewing behaviour of 8800 Australians.

They calculated that every hour of TV slices 22 minutes off the average life expectancy of an adult over the age of 25. Basically, people who watch 6 hours of TV a day can expect to die, on average, about five years younger than those who don’t watch any.

There are many other studies reaching similar conclusions. In a review of all the evidence, Dunstan’s team concluded that there was a “persuasive case” that excessive sitting “should now be considered an important stand-alone component of the physical activity and health equation”.

The message is pretty clear. Sitting down for hours at a time is a health risk, regardless of what you do with the rest of your day.

Just as you cannot compensate for smoking 20 cigarettes a day by cycling 20 miles at the weekend, a session of high-intensity exercise does not negate the effect of watching TV for hours at a time.

Patel’s study found that people who spent hours sitting had a higher mortality rate, even if they worked out for 45 to 60 minutes a day. The researchers call these people “active couch potatoes”.

But it is not just sitting down that worries them. It would appear that the harm comes first and foremost through the inactivity itself. Ignoring sleep, which brings its own health benefits, the researchers believe that other kinds of immobility may be just as dangerous as watching television, be it reading a book, working on a computer or sitting down at a desk.

To find out just how inactive people are, Dunstan equipped hundreds of subjects with accelerometers and inclinometers to monitor their daily activity. The accelerometers measured how energetic their movements were, and the inclinometers revealed how much time they spent sitting.

“The sobering reality,” Dunstan says, “is that across a 14 or 15-hour waking day, we’re getting 55 to 75% sedentary time. Moderate-to-vigorous activity – what people like to call ‘exercise’ – occupies just 5% or less of people’s days.”

From an evolutionary point of view, we are built to be active. Your grandparents did not have to go to the gym. They were simply active all day.

Further studies have revealed that inactivity produces a complex cascade of metabolic changes. For instance, muscles that aren’t used, not only waste away and weaken, but shift from endurance type muscle fibres, which can burn fat, to fast twitch fibres that rely more strongly on sugar.

Inactive muscles also lose mitochondria, which burn fat. With the muscles relying more on carbohydrates for what little work they are doing, unburned lipids accumulate.

Inactivity causes your blood to become fatty, which could be why sitting down has been linked to heart disease. Fat is also stored in muscles, the liver and the colon, places where it is not supposed to be.

Other changes involve insulin resistance, a diabetes-like condition in which glucose accumulates in the bloodstream even when the body produces insulin to remove it. All of this happens very quickly, in just three days you can become insulin resistant.

So what can you do to avoid this, other than quitting sedentary jobs and taking up hairdressing, becoming a postman or waiter?

First of all, it is important to realise that exercise is still beneficial. An hour in the gym cannot undo hours of sitting, but it is still good for your health.

But how?

Simply get up and move around more often.

This will raise your metabolic rate above 1.5 times the resting rate, this is considered light activity. Which means you are burning about 2 calories a minute.

By simply pacing around the room for a few minutes you can easily burn 20 calories. That’s also a really good way to clear the mind. People who get up and move around for 5 minutes every hour are every bit as productive as people who sit there for hours at a time.

The next step is to establish the best ways to build activity breaks into your day. Is it best for you to have frequent short breaks? Or have breaks less often but take longer ones? This will depend on your work schedule or what you have to get done during the average day.

Try standing up whenever you are on the phone. This has other benefits with regards to self esteem as well.

At home, the steps are the same. If you are sitting down at the computer, take a break and do the washing up or ironing.

If you are watching television, get up and move around every 20 minutes, or whenever there’s an ad break.

These steps will actually help you to reach your recommended daily exercise levels.

Anything is better than nothing. Just getting up and moving at all is taking a big step in the right direction.

And if you really want to take a step in the right direction, why not register for our free introductory module?