Think having a treadmill at your desk is a ridiculous fad? It may not be realistic for most workplaces but the idea is strongly rooted in science. You’re probably aware that sitting down all day is bad for your health. But just how bad? And is there anything you can do, short of quitting your desk job?

Regardless of how much exercise we do, it’s the hours of prolonged sitting that are killing us.

Conserving too much energy

As someone who has spent many years studying animals in the wild, I’m well aware most animals will conserve energy whenever possible. Fortunately I never had to do round-the-clock koala observations but I know someone who did and let’s say it wasn’t exactly riveting stuff.

But it seems in the western world, humans have taken energy conservation to such an extreme that our daily habit of sitting for hours is killing us.

Back in 1953, a paper published in the respected medical journal The Lancet, reported conductors on London buses had only half the chance of heart attack compared with the drivers of the same buses. The authors’ explanation for the huge differences among the 31,000 men studied? The conductors spent all day on their feet, walking the length of the bus and climbing stairs on the double-decker buses. The drivers spent all day sitting on their backsides.

We all need more exercise

The Australian Government Department of Health recommends adults aged 18–64 years spend 2.5–5 hours doing moderate intensity physical activity per week (or 2.5 hours of vigorous physical activity each week). At the same time, we should ‘minimise the amount of time spent in prolonged sitting’. I can’t imagine any of that is news to you.

What you may not know is that you can do all the vigorous exercise you want, but if you still spend too long sitting down every day, the health effects can be dire.

Exercising isn’t enough

It seems cruel that even when you get plenty of exercise something as simple as sitting down can be so bad. But research suggests too much sitting is quite distinct from too little exercise. Research shows that two hours of sitting down can be just as bad for us as 20 minutes of exercise is good for us.

When we spend hours each day sitting (on average we spend 8 – 9 hours per day sitting while we drive, work, eat, watch TV or read), we are at increased risk of obesity, abnormal cholesterol, high blood pressure, back injury, diabetes and heart disease. Too much sitting has even been linked to increased risk of developing cancer of the lung, colon and in women, the endometrium. What’s more, the more time you spend sitting each day, the more at risk you are of premature death from any cause, regardless of how much exercise you do.

How much more at risk? In an Australian study of 220,000 people, those who sat for more than 8 hours each day had a 15% greater chance of dying in the next three years than those who sat for fewer hours per day.

Put another way, every additional hour people spent watching TV each day resulted in an 11% increase in the risk of dying. These results were true regardless of how much people exercised, their age, sex and waist circumference and whether and how much they drank and/or smoked.

Of course, part of the problem is that the hour you spent watching the latest episode of Game of Thrones is an hour you could have spent exercising. But it is much more than that.

Even on days we exercise, our muscles are spending too much time inactive. This is known as the Active Couch Potato phenomenon. In 2012, Finnish researchers asked their volunteers to wear shorts that contained flexible electrodes. So rather than relying on people keeping their own tallies of hours spent exercising or sitting (or using accelerometers), the shorts continuously measured the activity of the hamstring and quadriceps muscles.

Surprisingly, there was no difference in the amount of time spent sitting on days the Finns exercised compared with days they didn’t. It seems that on days we do our planned exercise, we tend to take it a bit easier the rest of the day.

So why is sitting still so bad for our muscles? Because when our muscles don’t contract often enough, instead of being pumped back to the heart, blood can pool in our legs. This causes damage to our arteries and results in blood vessels that can’t shunt blood around our bodies effectively anymore.

No-one can argue with the evidence: sitting down a lot is very bad for your health.

The solution is dumbbell free

Of course we should still prioritise getting enough vigorous exercise.

But we now know that just as important is breaking up our sitting time. Research that came out of the Baker IDI Heart and Diabetes Institute here in Melbourne shows that two minutes spent walking for every 20 minutes sitting has enormous benefits for our health. And the more breaks you take, the better it is for you.

Work out of Indiana University published last month found that three slow, five-minute daily walks were enough to counter the negative effects on your leg arteries of three hours of sitting.

So make sure you still run, surf, go to the gym or rockclimb. But don’t underestimate the power of walking to your colleague’s desk instead of sending them an email, pacing the room while you talk on the phone or using the bathroom one floor up. Even fidgeting in your seat is better than sitting still.

If you can, convince your boss to get you a sit/stand desk and, when you’re not at work, try to sit still as little as possible.

Maybe sitting is the new smoking.

Links and stuff

• Australian Government Department of Health Physical Activity and sedentary Behaviour Guidelines
• Radio National Health Report on why you should break up long periods of sitting with activity
• A journalist’s experience of using a treadmill desk
• The Sitting is killing you infographic