Here is another study that shows TV times directly effects physical inactivity from Cardioblog. This is said as someone sitting here on a laptop, watching the TV, while blogging away. It would be nice to set up a spare TV downstairs so I can cycle as I watch TV. Some details:

The study monitored low-income residents in Boston, two-thirds of whom were overweight or obese. Participants used pedometers that documented inactivity associated with time spent watching TV.