We all know watching TV isn't good for us, but it turns out that it can actually kill you.
"High amounts of sedentary behaviour have been associated with increased risks of several chronic conditions and mortality." A recent article in the UK medical journal, The Lancet, describes "high amounts of sedentary behavior" as sitting for more than four hours per day - at work and at home (particularly watching tv). The study looked at several groups, including those who sat for more than 8 hours per day.
One finding was that people who exercised for 35.5 hours per week (the highest amount measured in the study) completely reversedor off-set the detrimental effects of prolonged sitting. Another finding was that the group who sat the least but who also exercised the least had an elevated occurrence of death and disease.
Watching tv is, apparently, especially deadly: "Watching TV for 3 h or more per day was associated with increased mortality regardless of physical activity, except in the most active quartile, where mortality was significantly increased only in people who watched TV for 5 h/day or more...." Meaning, one has to be moderately exercising for 6 hours a day to off-set the detrimental effects of watching TV just 3 hours a day! And even those who manage a 40-hour exercise regimen per week aren't undoing the damage of sitting and watching TV for 5 hours per day.
"High levels of moderate intensity physical activity (ie, about 60–75 min per day) seem to eliminate the increased risk of death associated with high sitting time. However, this high activity level attenuates, but does not eliminate the increased risk associated with high TV-viewing time. These results provide further evidence on the benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work ...."
The takeaway from this article (linked below) is that our largely-sedentary work lives take a toll on our health, but that can be reversed with even a moderate increase in moderate exercise. But watching TV is particularly pernicious: it takes double the viewing time in moderate activity to undo the damage, and that's only if we stop watching at the 3-hour-per-day mark. Higher than that and no amount of moderate exercise will reverse those effects.
Moderate activity is anything that elevates your heart rate but still allows you to carry on a conversation. If you're winded enough to not be able to maintain a conversation, that's more active than "moderate." So take a brisk walk on your lunch break. Take the stairs instead of the elevator. Take the long route to the meeting. Walk or bike to or from work (even just part of the way). In the words of a corporate slogan: Just do it.