Well, this is no big surprise. Watching television for several hours a day significantly increases the risk of life-threatening conditions like cardiovascular disease and diabetes 2. In fact, the overall mortality rate of heavy TV watchers for all diseases is higher than that of non-TV watchers. These findings are based over 40 years of data compiled by researchers at Harvard School of Public Health and collected in a survey published in this month's Journal of the American Medical Association. We'll dig into the details a bit, but you might want to turn off any nearby TVs before continuing to read--the conclusions are not encouraging.

The correlation between sedentary activities like watching TV and health risks has long been known, but according to the JAMA study, more than two hours a day of TV increases the risk of diabetes and cardiovascular disease by a troubling 20 percent and 15 percent respectively. More than three hours a day raises the risk of premature death for all other conditions by 13 percent. "Beyond altering energy expenditure by displacing time spent on physical activities, TV viewing is associated with unhealthy eating (e.g., higher intake of fried foods, processed meat, and sugar-sweetened beverages and lower intake of fruits, vegetables, and whole grains) in both children and adults," write authors Frank Hu and Anders Grøntved, who studied all relevant medical literature from 1970 to March 2011. 

It gets worse. "Future research should also look into the effects of extensive use of new media devices on energy balance and chronic disease risk," says Anders "No-Fun-Police" Grøntved. No but seriously, go exercise.