As you're no doubt sick of hearing by now, sitting is bad for your health. A group of Australian researchers recently tried to find out just how bad by analyzing data from a giant lifestyle survey with 11,247 participants over the age of 25. Every daily hour of sitting while watching TV was associated with an 8 percent higher risk of death, they reported in the October issue of the British Journal of Sports Medicine (they controlled for the effect of exercise, diet, obesity and other relevant factors). "Watching one hour of TV above age 25 may be about as lethal as smoking one cigarette," says J. Lennert Veerman, PhD, a senior research fellow at the University of Queensland, who led the study. Keep in mind that smoking causes many cancers—lung, throat, kidney, bladder, pancreas, stomach and cervix—as well as acute myeloid leukemia, and Veerman adds that it's also highly addictive. Then again, prolonged sitting has been associated with higher risks of heart disease, diabetes and obesity-related illness.
Best advice: Lighting up might be worse for us as individuals, but sitting down may well cost more lives overall. "While smoking rates are going down, almost everyone watches quite a bit of TV," says Veerman. He recommends limiting couch time to two hours per day or night.