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Physical inactivity is estimated to account for 6% of global deaths (1), and is associated with risk of Metabolic Syndrome and cancer (2,3,4).
Approximately 100,000 new cases of breast and colon cancer each year are linked to sedentary lifestyles (5). Another study found that taking frequent breaks from sitting is associated with smaller waist circumference and lower levels of C-reactive proteins, both biomarkers associated with elevated risk of some cancers for post-menopausal women (6).
The National Health and Nutrition Examination Survey (7) analyzed data of 4,757 participants and found that even short periods of light activity (standing up and walking for at least a minute) – reduced biomarkers such as large waist circumference, elevated triglyceride levels and increased insulin resistance.
There’s also a risk of heart disease and premature death from any cause increases for those spending more than four hours a day sitting. A study (8) with 4,512 subjects, found a 48% increased risk of all-cause mortality and an approximately 125% increase in risk of cardiovascular events for those spending more than four hours sitting. The risk was found to be independent of other detrimental factors such as smoking, hypertension, BMI, and social class.
Another study from Australia show that prolonged sittingis significantly associated with higher all-cause mortality riskindependent of physical activity. From a population study of 222 497 subjects, it was suggest that sitting time sitting was responsible for 6.9% of deaths (9).
Being inactive for more than 23 hours per week had a 64% greater risk of deathfrom cardio vascular disease than being sedentary for less than 11 hours per week (10). Sitting in one position for too long may develop blood clots, which are estimated to be a cause of death for up to 100,000 people per year (11).
A large Canadian Fitness survey (12) looked at more than 7000 men and nearly 10.000 women over a 12-year period, and the participants ranged from 18 to 90 years. The research found a significant link between time spent seated and mortality, and that being active doesn’t balance out the negative effects.
The physiology
Prolonged sitting disrupts metabolic health, increases plasma triglyceride levels and decreases levels of high-density lipoprotein cholesterol, increases insulin resistance (3,13) and affects carbohydrate metabolism (3).
Studies have used radioactive triglyceride tracers to examine metabolic effects of not standing on specialized leg muscles, such as the deep red quadriceps, that are designed for postural support (not all muscles have this same function). These muscles quickly lost more than 75% of their ability to siphon off the fat circulating in the lipoproteins from the bloodstream when incidental contractile activity was reduced. This was related to a 90% to 95% loss of lipoprotein lipase (LPL) activity locally in the most oxidative skeletal muscles in the legs, which are specialized for postural support (14).
In addition, sitting appears to lead to about a 20% reduction in high-density lipoprotein, or good cholesterol, increasing the risk of suffering from a cardiovascular disease (15). Remaining sedentary for more than 24 hours impairs the ability of insulin to uptake glucose, raising the risk of diabetes (16).
“We just aren’t really structured to be sitting for such long periods of time, and when we do that, our body kind of goes into shutdown. If there’s a fountain of youth, it is probably physical activity. So the problem isn’t whether it’s a good idea, the problem is how to get people to do more of it” Dr. Toni Yancey.
Sitting trains the body to do nothing and leads to physiological adaptations that reduce functionality.
Non-exercise activity thermogenesis (NEAT)
Sedentary behavior must be reduced, particularly reducing the long, uninterrupted bouts of inactivity. One method is engaging in non-exercise activity thermogenesis (NEAT).
Nonexercise activity thermogenesis (NEAT) is the energy expended for everything that is not sleeping, eating, or sports-like exercise. It includes the energy expended walking to work, typing, performing yard work, undertaking agricultural tasks, and fidgeting (17).
In 2005 Levine et al (18) published detailed results of his analysis of metabolism. Levine tracked food consumption and every activity using motion tracking underwear, he measured their body postures and movements every half-second for 10 days. Those who didn’t gain weight moved more than others, while eating the same, due to a difference of minus 2 hours sitting each day on average. The study suggested that “adopting the NEAT-enhanced behaviors of lean counterparts, might expend an additional 350 calories (kcal) per day.”
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References:
1. World Health Organization. Global Health Risks: Mortality and Burden of Disease Attributable to Selected Major Risks. Geneva, Switzerland:WHOPress; 2009.
2. Proper KI, Singh AS, van Mechelen W, Chinapaw MJM. Sedentary behaviors and health outcomes among adults: a systematic review of prospective studies. Am J Prev Med. 2011;40(2):174-182.
3. Tremblay MS, Colley RC, Saunders TJ, Healy GN, Owen N. Physiological and health implications of a sedentary lifestyle. Appl Physiol Nutr Metab. 2010;35(6):725-740
4. Grøntved A, Hu FB. Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a meta-analysis. JAMA. 2011;305(23): 2448-2455.
5. Research presented in November, 2011 at the American Institute for Cancer Research's (AICR) annual conference. The AICR presented data suggesting that about 100,000 new cases of breast cancer and colon cancer per year can be associated with physical inactivity.
6. Christine M. Friedenreich, Heather K. Neilson. Inflammatory Marker Changes in a Yearlong Randomized Exercise Intervention Trial among Postmenopausal Women. Cancer Prev Res (Phila). 2012 Jan;5(1):98-108.
7. Genevieve N. Healy Charles E. Matthews, David W. Dunstan, Elisabeth A.H. Winkler, Neville Owen. Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003–06. Eur Heart J. 2011 Mar; 32(5):590-7.
8. Screen-Based Entertainment Time, All-Cause Mortality, and Cardiovascular Events. Journal Americal College of Cardiology. 2011; 57(3):292-299
9. Sitting Time and All-Cause Mortality Risk in 222 497 Australian Adults. Arch Intern Med. 2012;172(6):494-500
10. Tatiana Y. Warren, Vaughn Barry, Steven P. Hooker, Xuemei Sui, Timothy S. Church, and Steven N. Blair. Sedentary Behaviors Increase Risk of Cardiovascular Disease Mortality in Men. Med Sci Sports Exerc. 2010 May ; 42(5): 879–885
11. Steven K. Galson. Prevention of deep vein thrombosis and pulmonary embolism. Public Health Rep. 2008 Jul-Aug; 123(4): 420–421
12. Katzmarzyk PT, Church, TS, Craig, CL, Bouchard C. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Med Sci Sports Exerc. 2009; 41(5):998-1005.
13. Hamilton MT, Hamilton DG, Zderic TW. The role of low energy expenditure and sitting on obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes. 2007; 56:2655–2667.
14. Hamilton, Marc T., Healy, Genevieve N., Dunstan, David W., Zderic, Theodore W. Owen, Neville. Too little exercise and too much sitting: inactivity physiology and the need for new recommendations on sedentary behavior. Current Cardiovascular Risk Reports. 2008, 4: 292-298.
15. Genevieve N, Dunstan, David W, Jo Salmon, Jonathan E Shaw, Paul Z, Owen, Neville. Television Time and Continuous Metabolic Risk in Physically Active Adults. Med Sci Sports Exerc. 2008 Apr;40(4):639-45.
16. Brooke R. Stephens, Kirsten Granados, Theodore W. Zderic, Marc T. Hamilton, Barry Braun. Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake. Metabolism. 2011 Jul;60(7):941-9
17. Levine JA. Nonexercise activity thermogenesis (NEAT): environment and biology. Am J Physiol Endocrinol Metab. 2004 May; 286(5):E675-85
18. Levine JA, Lanningham-Foster LM, McCrady SK, Krizan AC, Olson LR, Kane PH, Jensen MD, Clark MM. Interindividual variation in posture allocation: possible role in human obesity. Science. 2005 Jan 28;307(5709):584-6.
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