Researchers have uncovered a strong – but not surprising – link between television watching and life expectancy.

Data from the U.S. National Health and Nutrition Examination Survey (NHANES) for 2005-06 and 2009-10 was used to determine the amount of time that American adults spend watching TV and sitting down each day. Researchers crunched those numbers with findings from studies that examined the link between the amount of time people spend sitting and deaths from all causes.

Their conclusion? That limiting the amount of TV watching to less than three hours a day, adults could enjoy an extra two two years of life.

The findings were published online July 9 in the journal BMJ Open.

"The results of this study indicate that extended sitting time and TV viewing may have the potential to reduce life expectancy in the U.S.A.," the researchers wrote.

The NHANES data showed that American adults are involved in sedentary pursuits for 55 percent of their day, on average, which means that major population-wide behavioral changes are needed in order to achieve notable improvements in life expectancy, the researchers noted.

A number of previous studies have linked a lot of time sitting or watching TV with poor health, such as diabetes and death from heart disease and stroke.