You can now add desk jobs to one of the riskier career choices. A recent study has found that sitting for long periods of time increases your risk of dying.

Australian researchers found that the more people sit each day the greater their chances of dying early. People who sit for more than 10 hours a day has a 48 percent increased risk of death compared to people who only sit for less than four hours a day. Even exercising was not enough to offset the effects of sitting on your butt for several hours.

The study which began in 2006 and involved more than 200,000 men and women in NSW will be presented at the annual meeting of the 45 and Up Study, the largest ongoing health research project in the southern hemisphere on Thursday.

Professor Adrian Bauman, of the University of Sydney's school of public health and co-author of the study said people who are physically active in their jobs have a better chance of survival than desk jockeys.

"Your lowest risk of death is if you are physically active and don't sit," Professor Bauman said.

"Your highest risk is if you don't do any physical activity and you sit a lot of the day.

"If you think about a few hours of TV every day and driving to and from work and at work mostly sitting, it's not hard to get into that 10-11 hour-a-day range.

"What we have to do is work quite hard to undo that."

Office workers who spend most of their days chained to a desk should at least incorporate physical activity into their routines.

"People doing high amounts of physical activity, and that's an hour a day, are mostly offsetting the effects of sitting but few of us can get to that and struggle to reach the Australian recommended levels of half an hour (of exercise) a day," he said.

"The more you sit in the day the more you should try and build in a few extra minutes of physical activity by walking to the bus stop or to the sandwich shop at lunchtime and using the stairs instead of the lift."

It's still unclear why sitting down is so bad for your health but one theory points to the effect sitting has on blood-sugar levels.

"What's happening is when you sit, the meal you have just eaten is broken down into sugar and your blood sugar stays high," Bauman said.

"Sugar wants to be taken into muscles and the liver to be used but if you're sitting it's just circulating so your blood sugar stays high."