Adults who sat eleven or more hours a day are at an increased risk of dying compared with those who sat for fewer than four hours a day, says study.
"That morning walk or trip to the gym is still necessary, but it's also important to avoid prolonged sitting," the paper quoted study author Dr. Hidde van der Ploeg, of the University of Sydney's School of Public Health, as saying in a statement.
According to him, their results suggest the time people spend sitting at home, work and in traffic should be reduced by standing or walking more.
A similar report was published by The British Journal of Sports Medicine last fall, which highlighted a link between prolonged sitting and health.
The report looked at Australian adults in 2008, and concluded that those who watch TV an average of six hours a day will live 4.8 years fewer than those who don't.
While taking into consideration age, diet and exercise habits, the study found that those with the "highest sedentary behavior" had the greatest risk for cardiovascular disease, diabetes and dying prematurely.
It means adults older than 25 who watch a single hour of TV will see their life expectancy shorten by 21.8 minutes.
But a single cigarette reduces life expectancy by about 11 minutes, the study said.
"Sitting is the new smoking," said Dr. Anup Kanodia of Ohio State University's Wexner Medical Center.
Experts say sitting down could be worse because you're not burning nearly as many calories as if you were standing, plus a typical day of sitting suppresses the production of a molecule called lipoprotein lipase, which would otherwise metabolize fats and sugars.