Millions of American workers spend most of their day inactive. We may spend eight hours sitting at a desk in front of a computer. All this sitting turns out to be deadly. Researchers in the growing field of sedentary physiology have found the inactivity more than diet may be to blame for our nation’s overall poor health and the obesity epidemic. And even exercising after work — say you drop off at the gym on your way home — cannot counteract the ill effects of resting on your rump all day long. Today on Radio Times, how our sedentary lifestyle is killing us. First, we’ll take a look at the active lives of our ancestors. Harvard professor of human evolutionary biology DANIEL LIEBERMAN walks us through a day in the life of a hunter-gatherer – do you think you could keep up? And we talk with Mayo Clinic obesity researcher JAMES LEVINE about his inactivity studies and health effects of too much sitting.