There's good news for office-workers, with a study finding one hour of daily exercise can offset the risks associated with sitting at a desk for hours.

Just one hour of brisk walking a day could eliminate the harmful health risks of sitting on your toosh all day, a global study has found.

Researchers analysed the activity levels of one million people from Australia, the US and Western Europe in a bid to work out how many hours of daily physical activity is required to offset prolonged periods of sitting.

They classified the individuals, of an average age of 45, into four equally sized groups according to how active they were - less than five minutes a day for the least active, and up to 60-75 mins a day for the most active.

It was found people who sat for eight hours a day but were physically active had a much lower risk of death from chronic disease compared to those who sat for fewer hours but were not physically active.

The authors of the report, published in The Lancet, say this suggests that physical activity is important no matter how many hours a day are spent sitting.

In fact, the increased risk of premature death associated with sitting for eight hours a day was eliminated for people who did a minium of one hour of physical activity per day.

Those at greatest risk of premature death were the people who sat for long periods of time and were inactive.

The WHO guidelines only recommend that adults do at least 150 mins of physical activity per week - which is much lower than the 60-75 minutes per day identified in this analysis.

Physical inactivity is linked to an increased risk of heart disease, diabetes and some cancers.

Professor Ulf Ekelund from the Norwegian School of Sports Sciences says this research is good news for the thousands of people who commute to work and have office-based jobs - those who just can't escape sitting for prolonged periods of time.

"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 recommended but if this is unmanageable, some exercise each day is still beneficial, Prof Ekelund said.

Reducing time spent sitting watching TV can also help.

The study also found that more than three hours of this sedentary behaviour was associated with an increased risk of death from chronic disease in all activity groups, except the most active.