Office staff should take a stand for health by refusing to sit down at meetings and moving their work station to the nearest filing cabinet, according to an expert.
Professor Stuart Biddle spelled out his advice after research showed that lounging in a chair for too long can double the risk of diabetes, heart disease and death.
The findings indicate that sitting is bad in itself, irrespective of other time spent exercising or playing sport.
Scientists analysed the results of 18 studies with a total of 794,577 participants and found a big difference in health outcomes between the most and least sedentary.
Prof Biddle, from the University of Loughborough, who was one of the researchers, said: "Currently society forces us into too much sitting, sitting at school, sitting at office desks, sitting in cars and so on.
"There are many ways we can reduce our sitting time, such as breaking up long periods at the computer at work by placing our laptop on a filing cabinet. We can have standing meetings, we can walk during the lunch break, and we can look to reduce TV viewing in the evenings by seeking out less sedentary behaviours."
Prof Biddle practices what he preaches. He has a reminder note on his white board at work that says: "first 15 minutes of a meeting standing up".
He added: "I get a few odd looks - sometimes people think you're nuts or assume you have a bad back. But I've had quite a lot of positive feedback too. Standing up at a meeting makes you appear more animated and seems to make a good impression.
"I did go to one external meeting where everyone was sitting down as usual and I told them they should be standing a bit more. By the end of the meeting nearly everybody was standing and they seemed to quite like it."
He advocates the use of "standing desks" which can be raised or lowered and are mainly designed for people with back problems.
"You can have a posh electrically operated version or a hand-cranked one, or you can create your own standing desk by putting your screen a little higher, for instance on top of a filing cabinet," he said.
The study, published in Diabetologia, the journal of the European Association for the Study of Diabetes, analysed research data on people with different levels of sedentary behaviour.
Compared with the least sedentary, those who spent the most time sitting down had a 112% greater risk of diabetes.
Similarly, the risk of cardiovascular events such as heart attacks or strokes was increased by 147% in the most sedentary, and death linked to heart disease by 90%.
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Prof Biddle said it was not possible from the study to say how much time spent sitting is too long.
But he pointed out: "As a rule of thumb, if you can break up sitting time by at least five minutes every half hour we think that will benefit you.
"What we're seeing is these negative effects that are independent from the physical activity we do, and that's really crucial. So you can go for a 30 minute run every day but if you're sitting around for the rest of the day you're not doing yourself any favours."
The research suggests that despite the stress and discomfort, commuting to work on packed trains or buses might have some health benefits.
"It's likely that you get more walking and standing on a commute to work than if you travel by car," said Prof Biddle.
Study leader Dr Emma Wilmot, from the Diabetes Research Group at the University of Leicester, said: "The average adult spends 50% to 70% of their time sitting so the findings of this study have far reaching implications. By simply limiting the time that we spend sitting, we may be able to reduce our risk of diabetes, heart disease and death."
The idea that sitting down might be bad for health dates back to the 1950s, when researchers found London bus drivers were twice as likely to suffer heart attacks than conductors.
It was assumed this was because bus conductors benefited from being active and moving around. Less attention was paid to the negative effect of drivers sitting for long periods of time in their cabs.
The scientists wrote in their paper: "In the following 60 years research has focused on establishing the links between moderate-to-vigorous intensity physical activity and health, largely overlooking the potentially important distinction between sedentary (sitting) and light-intensity physical activity."
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