I wonder, too, if it isn’t the sitting rather than the TV that is the problem.
Two guys have a site called Obesity Panacea, and its focus is primarily the health hazards associated with prolonged inactivity. They cite a study that says the same thing - exercising for an hour or so a day and spending the rest of the day sedentary is not healthy. Standing is better than sitting, and movement, even low-level, is best.
So, maybe I should go clean my house instead of sitting here goofing off here at Free Republic. ;-)
I think it is the sitting....the article talks more about the long period of inactivity more than the television.
We sometimes ride an exercise bike while watching television, and I think if you kind of broke up the evening (say rest on the butt for an hour after dinner, than get on the bike for an hour, then rest for an hour and then finish off with 30 minutes of bikiing before bed) would probably nullify the negative health effects.
It appears 4 hours of complete inactivity is the really bad point, while 2 is much less serious.