(CNN)One of your favorite activities may actually be killing you. Our entire modern world is constructed to keep you sitting down. When we drive, we sit. When we work at an office, we sit. When we watch TV, well, you get the picture. And yet, a new study that’s running in the Annals of Internal Medicine found that this kind of sedentary behavior increases our chances of getting a disease or a condition that will kill us prematurely, even if we exercise.