How much exercise you should be doing if you sit at a desk all day. It's way more than we've been told.

We’ve been told our office jobs are killing us. Sitting down at a desk all day is bad for our health, our waistline, our posture.

So it’s a good day when you find out there are changes you can make that don’t just involve investing in a trendy standing or treadmill desk. Not so good when you find out you’ve seriously got to step up your exercise regime.

Researchers have concluded in a major new Lancet study that doing an hour of exercise a day could combat all the dangers associated with sitting at a desk for eight hours.

“High levels of moderate intensity physical activity (ie. about 60-75 min per day) seem to eliminate the increased risk of death associated with high sitting time,” the study states.

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Happily, this hour of activity can be merely brisk walking or cycling — so, no, you don’t need to be sweating bullets at the gym every day.

The scientists examined results of over one million people from the US, Europe and Australia across 16 studies to reach their conclusions.

Physical inactivity has been linked to an increased risk of heart disease, diabetes and some cancers. It’s associated with a staggering more than five million deaths per year. It also costs the global economy over US$67.5 billion per year in health care costs and lost productivity.

The Lancet research states that people who sit for eight hours a day but are physically active have a much lower risk of death compared to people who sit for fewer hours a day, but are not physically active.

This suggests that exercise is vital even if the hours spent sitting each day are less.

The greatest risk of death was for people who sat for long periods of time and were inactive.

Watching TV for more than three hours a day was also linked to a higher risk of death in people who didn't manage to bust out an hour of exercise.

WHO guidelines recommend 150 minutes of exercise per week, which is much lower than the daily 60-75 minutes advised by Lancet.

Researchers also warn that a worrying 25 per cent of people in their analysis were doing an hour of daily physical activity and are calling for measures to increase this figure.

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“There has been a lot of concern about the health risks associated with today’s more sedentary lifestyles,” says lead author Professor Ulf Ekelund.

“Our message is a positive one: it is possible to reduce – or even eliminate – these risks if we are active enough, even without having to take up sports or go to the gym.”

Ekelund, who is from the Norwegian School of Sports Sciences and UK's University of Cambridge, acknowledges that for many people there is no way to escape sitting for prolonged periods.

"For these people in particular, we cannot stress enough the importance of getting exercise, whether it’s getting out for a walk at lunchtime, going for a run in the morning or cycling to work. An hour of physical activity per day is the ideal, but if this is unmanageable, then at least doing some exercise each day can help reduce the risk," he says.