"...the amount of leisure time spent sitting in front of a screen can have such an overwhelming, seemingly irreparable impact on one’s health that physical activity doesn’t produce much benefit.....those who said they spent two or more leisure hours a day sitting in front of a screen were at double the risk of a heart attack or other cardiac event compared with those who watched less. Those who spent four or more hours of recreational time in front of a screen were 50 percent more likely to die of any cause. It didn’t matter whether the men were physically active for several hours a week — exercise didn’t mitigate the risk associated with the high amount of sedentary screen time....One possible mechanism, demonstrated in animal studies, is that being sedentary may affect lipid metabolism. Prolonged inactivity appears to sharply reduce the activity of an important enzyme called lipoprotein lipase, which is responsible for breaking down circulating blood lipids and making them available to muscles for energy....Lowered enzyme activity leads to higher levels of fats and triglycerides in the blood, and to a higher risk of cardiovascular disease. Exercise has very little impact on the enzyme’s activity...Extended sitting may also lead to high levels of low-grade inflammation, which can also lead to heart disease...The study focused on recreational screen time because it’s the easiest to curtail, Dr. Stamatakis said. But he encouraged employees who work at computers all day to get up and take breaks and short walks periodically."
Link to full article: http://well.blogs.nytimes.com/2011/01/12/the-hazards-of-the-couch/