Actually, I can see arguments that it is all four of those. 1) Being sedentary is not directly addictive, but it is self-perpetuating. Being sedentary reduces

Actually, I can see arguments that it is all four of those. 1) Being sedentary is not directly addictive, but it is self-perpetuating. Being sedentary reduces your overall energy levels, and that leads to more sitting. There are also a ton of psychologically addictive activities that require sitting. 2) What about playing video games, watching movies, Facebook (or whatever the kids do these days), etc.? And don't forget studying. We actually force teenagers to sit for 6-9 hours a day for 75% of the year. 3) There's a good bit of evidence that supports that chronic sitting does, in fact, cause long term harm. 4) What's cheaper than sitting?