Americans might live longer if they cut back on the amount of time they spend sitting down, a new study says.

Reducing the daily average time that people spend sitting to less than three hours would increase the U.S. life expectancy by two years, the study found. And reducing the time spent watching TV to less than 2 hours daily would increase life expectancy by 1.4 years.

The study adds to a growing body of evidence suggesting that sitting itself is deadly. Study researcher Peter Katzmarzyk, of the Pennington Biomedical Research Center in Baton Rouge, La., said the research "elevates sedentary behavior as an important risk factor, similar to smoking and obesity."

Other studies have found our culture of sitting may be responsible for about 173,000 cases of cancer each year.

Because U.S. adults spend, on average, between 4.5 and five hours a day sitting down, a significant shift in the population's behavior would be needed to have an effect on life expectancy, Katzmarzyk said. This might be achieved through changes at the workplace, such as the use of standing desks, and by watching less TV, he said.

Read more from MSNBC.