Sitting kills but being fit might help keep you safe: new study.

Image: ABC. By Cathy Johnson. 

Looking for motivation to get fit? An important new study by Norwegian and Australian exercise scientists may just do the trick.

Not only is it true that the fitter you are, the less likely it is you’ll die of pretty much any health condition you can name.

But being fit may be enough to compensate for the health risks posed by extended sitting — a finding that seems to contradict what we’ve been told about sitting’s harms for years.

The finding, based on a study of more than 26,000 people, relates to one of the scarier bits of health news of the last decade — that sitting for long periods raises your odds of developing diabetes, heart disease and some cancers, as well as of dying early from any cause.

When we sit, our leg and trunk muscles are inactive and this can lead to a potentially-harmful build-up of sugars and fats in our blood.

Worse still, we’ve been told being active at other times of the day was not enough to offset the health risks of sitting. So going for a run or to the gym after work would not make up for the damage to your body from spending the bulk of your day sitting at your desk.

But the new finding by researchers from Norwegian University of Science and Technology and the University of Queensland suggests sitting for more than seven hours a day may not necessarily be so harmful if you are fit. It is the first time this has been shown.

The study was published in Medicine & Science in Sport & Exercise, the official journal of the American College of Sports Medicine.

Move more and get fit

One of the authors, the University of Queensland’s Professor Jeff Coombes, believes the finding has “huge” implications for people who sit for long periods and want to know what to do to protect their health.

“It’s not just breaking up sitting time by walking around the office a bit, or standing up instead of sitting some of the time. They need to work on their fitness.

“You need to push yourself to an intensity where you puff and pant a bit [to build fitness],” he said.

But Australian sitting researcher Dr David Dunstan, who was not involved in the study, argued breaking up sitting time with little bits of activity, or just standing, was still important as it had been shown to improve some disease markers including blood pressure and blood glucose.

“Even if you’re exercising, if you’re also moving around more frequently during the day, you’re going to have a better health profile than the person who’s exercising and sitting on their backside all day.”

He said it might be good news if fit people can sit more, but most Australians are not fit and so for them, extended sitting was particularly harmful.

And it’s still the case that the more you can move around each day, even if it’s not making you puff and pant, the better for your health overall.

Professor Ulrik Wisloff, one of the Norwegian authors of the study, said he still recommended “all people sit less, have more walking-meetings, and stand more” to “improve energy balance and not gain more weight”.

But if you have higher fitness than average for your age group you may be on the “safe side” in terms of the effect sitting has on your disease and death risk.

You can get an idea of how good or bad your fitness is for your age using an online “fitness age” calculator the Norwegian researchers developed a few years ago.

Puff and pant for extra fitness

The study showed being physically active without having fitness offered no protection against the harms of sitting, Professor Coombes said.

While most of us think if we are active, we must be improving our fitness, this was not necessarily true.

While brisk walking could make you fitter “if you can chat easily with a friend while you’re walking, you’re probably not working hard enough”.

But exercising at a higher intensity, where it’s hard to speak more than a few words, would be building fitness, he said.

The study confirmed previous findings that 150 minutes a week of moderate intensity exercise (where you can talk but not sing) did not protect against the risks from long periods sitting. But the exact amount and intensity of exercise that would be protective isn’t known.

Associations not proof

Dr Dunstan, head of physical activity at Baker IDI Heart and Diabetes Institute, said the study was based on associations at one point in time and more evidence was needed before we can say that fitness is enough to undo sitting’s harms.

The research team made their findings after looking for correlations between the number of hours per day people spent sitting and their risk of heart disease (as measured by a cluster of factors including blood pressure, levels of glucose, cholesterol and other fats called triglycerides in the blood, and waist circumference).

They then looked to see whether the link between sitting time and heart disease risk changed, depending on how fit the people were.