The average adult in the USA and Australia spends more than 54% of their waking time sedentary . Sounds about right when you think about it, but what does it mean for our health and wellbeing, and what can you do to minimise the effect?
Long periods of inactivity have been shown to be detrimental, even among individuals who meet overall physical activity recommendations. Researchers have now recognised that the risks associated with periods of sedentary behaviour are independent to those resulting from a total lack of physical activity, leading to a new field of “sedentary physiology” .
Sedentary time has been associated with an increased risk of diabetes, cardiovascular disease and all-cause mortality (death by any cause).
"We now have some physiological studies showing that when you are sitting, your leg muscles (the largest in the body) are completely inactive, which causes problems with how you handle your blood sugar and how you handle cholesterol," says Peter Katzmarzyk, Sendentary Physiology Researcher at the Pennington Biomedical Research Centre .
A 2012 Australian study by the University of Queensland highlighted the relationship between sittings for long periods, and the resulting effect on a persons lifespan. The results showed that for every one hour of television watched (sitting) after the age of 25, the viewer’s life expectancy was reduced by 21.8 minutes. The research was adjusted for smoking, waist circumference, dietary quality, exercise habits and other variables, and has recently been since published in The British Journal of Sports Medicine. The study suggests that limiting your viewing to less than 2 hours a day may increase your life expectancy by 1.4 years .
A separate 2012 US study, published in the BMJ Open Medical Journal, suggests that limiting sitting to less than 3 hours per day may increase life expectancy by 2 years .
Sounds difficult to do, but don’t panic and quit your desk job just yet. Short bouts of physical activity used to break up sedentary behaviour can significantly reduce the adverse effects .
So, stand up and move around whenever you can. All the evidence points to the fact that even small changes can have significant impact of your health long term.
 Tremblay et al., 2010, “Physiological and health implications of a sedentary lifestyle” Applied Physiology, Nutrition, and Metabolism, 35, 725-740, 55(11), 2895-2905, accessed 31 January 2013, <http://www.sfu.ca/~leyland/Kin343%20Files/sedentary%20review%20paper.pdf>
 Wilmot et al. 2012, “Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis” Diabetologia, accessed 31 January 2013, <http://link.springer.com/article/10.1007%2Fs00125-012-2677-z>
 ABC. 2012, Sitting less may expand lifespan, accessed 31 January 2013, <http://www.abc.net.au/science/articles/2012/07/10/3542569.htm>
 The British Journal of Sports Medicine (Australian Diabetes, Obesity and Lifestyle Study) as cited by the NY Times, access 31 January 2013, <http://well.blogs.nytimes.com/2012/10/17/get-up-get-out-dont-sit/>
 Katzmarzyk, P & I, Lee. 2012, Sedentary behaviour and life expectancy in the USA: a cause-deleted life table analysis, BMJ Open, 2(4), accessed 31 January 2013, <http://bmjopen.bmj.com/content/2/4/e000828.full>
 Veerman, J.L. et al. 2012, “Television viewing time and reduced life expectancy: a life table analysis”, Br J Sports Med, 46(13), 927-930, accessed 31 January 2013 <http://bjsm.bmj.com/content/46/13/927.abstract>