American adults may boost their life expectancy by two years by sitting for fewer than three hours a day, researchers said Tuesday, while admitting this was a tough task.

Reducing television viewing to under two hours a day could similarly add 1.4 years, the US team said in a paper in the online journal BMJ Open.

A recent study found that US adults spend about 7.7 hours per day engaged in "sedentary behavior."

"Yes, this would be a challenge," co-author Peter Katzmarzyk of the Pennington Biomedical Research Centre told AFP of the team's proposal to reduce sitting -- given the amount of time most people spend behind their desks at work.

"On the other hand, there are many strategies to reduce sitting time, such as standing more at work using a standing desk or treadmill desk, having walking meetings, going to see someone down the hall rather than emailing them etc."

The research was based on a comparison of population health and lifestyle statistics with polling data on inactivity.

Other studies have linked extended periods of sitting or watching television to diabetes and death from heart disease or stroke.(AFP)