"Our bodies were not built for life in a chair and it is no surprise that research has highlighted the danger that so much sitting poses to health. Scientists have found that time spent sitting was associated with increased risk of mortality. Those who sat “most of the time” were more likely to die during the following 12 years than those who “almost never” sat, even after controlling for age, smoking, body weight and physical activity. Even if they exercised, people who sat for over 6 hours per day had a higher risk of death than those who sat for under 3 hours per day. Sitting watching television for an average of 6 hours a day could shorten life-expectancy by almost 5 years." (Conditioning Research blog, 2011)See the full article here, complete with other studies.
Conditioning Research. (2011). Sitting and Health. Retrieved 22/08/2011. http://conditioningresearch.blogspot.com/2011/08/sitting-and-health.html