An Australian study found adults who spends an average of six hours a day watching TV over the course of a lifetime can expect to live 4.8 years fewer than a person who does not watch TV.

In fact, every single hour of television watched after the age of 25 reduces the viewer’s life expectancy by 21.8 minutes. By comparison, smoking a single cigarette reduces life expectancy by about 11 minutes, the authors said.

The average adult spends 50 to 70 percent of their time sitting. What's even more surprising from this study was those who sat the most, had a 112 percent increase in risk of developing diabetes; a 147 percent increase in risk for cardiovascular disease; and a 49 percent greater risk of dying prematurely — even if they regularly exercised.

Why this might happen is still a mystery. But one reason might be that when muscles don’t contract, they require less fuel, and the surplus, in the form of blood sugar, accumulates in the bloodstream, contributing to diabetes risk and other health concerns. So, get up and start walking!

Click here for Gina Kolata's NYTimes story