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 sitting
is significantly associated with higher all-cause mortality risk
independent 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 death
from 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.
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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.
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Colley RC, Saunders TJ, Healy GN, Owen N. Physiological and health implications
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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
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A.H. Winkler, Neville Owen. Sedentary time and
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Hooker, Xuemei Sui, Timothy S. Church, and Steven N. Blair. Sedentary Behaviors Increase Risk of
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PT, Church, TS, Craig, CL, Bouchard C. Sitting time and mortality from all
causes, cardiovascular disease, and cancer. Med Sci Sports Exerc. 2009;
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obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease.
Diabetes. 2007; 56:2655–2667.
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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:
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Granados, Theodore W. Zderic, Marc T. Hamilton, Barry Braun. Effects of 1 day
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McCrady SK, Krizan AC, Olson LR, Kane PH, Jensen MD, Clark MM. Interindividual
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