Sitting down for too long can cause major health problems
ARE you sitting down? Don't get too comfortable, because mounting evidence suggests you're increasing your risk of heart disease, diabetes, cancer and premature death.
"If you've been sitting for 30 minutes or more you've been sitting too long," warns physical activity expert David Dunstan.
One recent Australian study found people who sit down for more than 11 hours a day are 40 per cent more likely to die early than those who do so for less than four hours.
It gets worse. Daily exercise doesn't appear to make any difference.
But the Australian professor has a simple solution.
"People can improve their health by breaking up their sitting time with frequent short breaks," he says.
All it takes is getting off your bum a few times every hour, and your "health profile" is likely to markedly improve.
In fact, Dunstan is on the verge of finding out if simply standing up will produce the same beneficial results.
"We just finished that study last week," he says. "I think in a few weeks when we start getting our teeth into the data we will be able to answer that question more definitively."
Dunstan certainly practises what he preaches. At the Baker IDI Heart and Diabetes Institute in Melbourne, he spends much of his day standing at a "height-adjustable work station".
That's in stark contrast to the majority of people in developed economies who spend more time sitting than sleeping.
Whether it's at the breakfast or dinner table, in the bus, train or car, at work or in front of the TV, most of us sit down far more than we stand up.
Office workers are the worst culprits, spending up to 80 per cent of the day glued to their seats.
To get more evidence of the toll that takes on their bodies, Dunstan is now testing almost 200 desk-bound federal government employees.
The control group are working as normal, while others have been given adjustable work stations and encouraged to move around more.
One of Dunstan's aims is to compare their bodies' metabolic reactions, and particularly how they process blood sugar and fats; key markers for increased risk of conditions like heart disease and cancer.
In a previous study, Dunstan discovered that a light two-minute walk every 20 minutes - the equivalent of going to the toilet or office kitchen - lowered blood glucose levels by around 25 per cent in overweight participants who had eaten a meal high in fat, sugar and calories.
Unlike those results, recorded over a five-hour period, his latest research is long-term, conducting health check-ups at the start of the trial, and then after three and 12 months.
Of particular interest will be changes in blood cholesterol and glucose. High levels are linked to long-term serious health consequences.
"It's probably to my knowledge one of the first studies to really start to look at biomarkers over a prolonged period," he said.
"I do think we'll be able to at least detect some changes. Whether or not they'll have clinical relevance over that period, I don't want to say yes or no at this stage."
Dunstan suspects the health benefits associated with short breaks can be attributed to a metabolic consequence of moving around.
Muscle contraction plays an important role in many of the body's regulatory processes, and acts in a similar way to insulin, helping transport glucose out of the blood and into the muscles.
"The simplest explanation is that when we're sitting we've got inactivity in our very large muscles like the muscles of the lower legs," he says.
"People are sitting for probably eight to nine hours of the day where the optimisation of that muscle contraction is absent.
"So the message is simple. We need to move our muscles more frequently during the day to assist our bodies."
But improved health requires a more flexible working environment.
Dunstan says adjustable work stations have been shown to reduce daily sitting time by up to two hours, but is encouraging participants in the government trial to embrace other changes like holding meetings standing up.
There are all manner of behavioural, cultural and organisational challenges to overcome, and public health authorities will require rigorous proof, but the professor envisions a workplace of the future unrecognisable from today.
Next week he will be in Adelaide for the Australian Heart Foundation's annual conference, and will listen with interest to the results of a stand@work study into the effectiveness of adjustable work stations in the organisation's NSW offices.
"We already know that changing from sitting to standing throughout the day is good from a postural point of view," says Dunstan.
"We're now saying the same for metabolic health. My message for people is to give it a try."