Watching TV for less than two hours a day can increase life-expectancy by more than a year, says a new study.

The study also reports that reducing the time spent just sitting to less than three hours a day can increase life expectancy by almost two years.

The results come from pooled data from various studies done on sedentary behaviour and life expectancy.

Researchers, Peter Katzmarzyk and I-Min Lee gathered data from all these studies to help determine "population attributable fraction," which shows how much the risk factor will affect a population. The PAFs for deaths from all causes linked to sitting time and TV viewing were 27% and 19%, respectively.

"The results of this study indicate that extended sitting time and TV viewing may have the potential to reduce life expectancy in the USA," authors of the present study wrote.

Not Just an American Problem

Health experts agree to the present study's findings and say that the problem of a sedentary lifestyle is not restricted just to America but affects many countries.

"It's extraordinary to see the coming to life of the concept that your chair really does appear to be killing you, one year after another." James Levine, a professor of medicine at Mayo Clinic in Rochester, MN who was not involved in this study, reported to USA Today.

"Sitting is diminishing the health of the nation. It's not just a problem here but also an issue in many other countries," Levine noted to USA Today.

Researchers say that the study results don't mean that anybody who watches television for more than 2 hours a day will die sooner than someone who is more active.

"This research only suggests a causal association between sedentary behavior and a shorter life expectancy. It also used American data so we'd need to see more research to understand what it means for the UK population," Natasha Stewart, senior cardiac nurse at the British Heart Foundation, who wasn't involved in the study, told BBC.

Previous research has shown that even children are spending more time sitting at home than playing outdoors. Experts say that an adult requires at least 30 minutes per day of physical activity to stay fit while children require at least 60 minutes of playtime.

"We all need to be regularly active to keep our hearts healthy. So whether it's by walking to the local shop rather than driving, or playing sport rather than watching it on TV, there are lots of ways to be more active and improve your health," Natasha Stewart told BBC.

Researchers found that in a study, participants reported that they spend more than half of their day on sedentary activities.

"Given that the results from objective monitoring of sedentary time in NHANES (National Health and Nutrition Examination Survey) has indicated that adults spend an average of 55% of their day engaged in sedentary pursuits, a significant shift in behavior change at the population level is required to make demonstrable improvements in life expectancy," the authors concluded in a statement.

According to UC Atlas of Global Inequality, despite spending more on health care than any other country, average life expectancy in US ranks at 27 in the world.

The study is published in BMJ Open.