In recent years the data gathered from large epidemiological studies have suggested that more time spent sitting correlates with higher mortality independently of the level of exercise undertaken by an individual. This association seems fairly robust as it has been replicated in a number of different data sets and by different research groups. Here is a survey of these results:
The amount of time a person sits during the day is associated with a higher risk of heart disease, diabetes, cancer, and death, regardless of regular exercise. "More than one half of an average person's day is spent being sedentary - sitting, watching television, or working at a computer. Our study finds that despite the health-enhancing benefits of physical activity, this alone may not be enough to reduce the risk for disease." The meta-analysis study reviewed studies focused on sedentary behaviour. The authors found the negative effects of sitting time on health, however, are more pronounced among those who do little or no exercise than among those who participate in higher amounts of exercise.
"The findings suggest that the health risk of sitting too much is less pronounced when physical activity is increased. We need further research to better understand how much physical activity is needed to offset the health risks associated with long sedentary time and optimize our health." Future research will help determine what interventions, in addition to physical activity, are effective against the health risk of sedentary time. "Avoiding sedentary time and getting regular exercise are both important for improving your health and survival. It is not good enough to exercise for 30 minutes a day and be sedentary for 23 and half hours."