Sitting less than 3 hours a day may extend American lives, reveals study.
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 behaviour".
"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.
"We now have some physiological studies showing that when you are sitting, your leg muscles (the largest in the body) are completely inactive, which causes problems with how you handle your blood sugar and how you handle cholesterol," Katzmarzyk said by email.
"The results of this study indicate that extended sitting time and TV viewing time may have the potential to reduce life expectancy in the USA," added the study.
"... a significant shift in behaviour change at the population level is required to make demonstrable improvements in life expectancy."
The paper stressed this was a theoretical estimate, and should not be taken to mean that people who are less active should expect to live 1.4 or two years fewer than the rest.
"Life expectancy is a population statistic and it does not apply to individuals."
The study used US population data and could not be applied to other countries, Katzmarzyk said.