Very helpful.


--- On Thu, 13/1/11, Edgar Owen <> wrote:

From: Edgar Owen <>
Subject: [Zen] News: Can sitting too much kill you?
Date: Thursday, 13 January, 2011, 8:22 PM



      For all you deluded ones who believe that sitting instead of daily life 
is Zen. 



Can sitting too much kill you?By Travis Saunders | Jan 6, 2011 10:39 AMWe all 
know that physical activity is important for good 
health—regardless of your age, gender or body weight, living an active 
can improve your quality of life and dramatically reduce your risk of death and 
disease. But even if you are meeting current physical activity guidelines by 
exercising for one hour per day (something few Americans manage on a consistent 
basis), that leaves 15 to 16 hours per day when you are not being 
active. Does it matter how you spend those hours, which account for more than 
90% of your day? For example, does it matter whether you spend those 16 hours 
sitting on your butt, versus standing or walking at a leisurely pace? 
Fortunately or unfortunately, new evidence suggests that it does 
matter, and in a big way.What is sedentary behavior?Before we go any further, 
it’s important that we define the term "sedentary 
behavior". Sedentary behavior is typically defined as any behavior with an 
exceedingly low energy expenditure (defined as <1.5 metabolic equivalents). 
In general, this means that almost any time you are sitting (e.g. working on a 
computer, watching TV, driving) or lying down, you are engaging in sedentary 
behavior. There are a few notable exceptions when you can be sitting or lying 
down but still expend high energy expenditure (e.g. riding a stationary bike), 
but in general if you are sitting down, you are being sedentary.The above 
definition may seem rather intuitive, but this is not the way that 
the term sedentary has been used by exercise science researchers for the past 
years. Up until very recently, referring to someone as sedentary meant simply 
that they were not meeting current guidelines for physical activity. In simple 
terms, if you were exercising for 60+ minutes/day, you were considered 
physically active. If you were exercising 10 minutes/day, you were sedentary. 
Case closed. But as we will discuss below, sedentary time is closely 
associated with health risk regardless of how much physical activity you 
on a daily basis. Further, it is entirely possible to meet current physical 
activity guidelines while still being incredibly sedentary. Thus, to quote 
researcher Marc Hamilton, sitting too much is not the same as exercising 
too little. (if you take only one thing from this post, let it be that 
quote from Dr Hamilton). Which is why it is so important that when we use the 
term "sedentary", we are all on the same page about what that means.Now that we 
know what sedentary behavior is, let’s look at its relationship 
with health risk.Epidemiological EvidenceIn 2009 Dr Peter Katzmarzyk and 
colleagues at the Pennington Biomedical 
Research Center published an influential longitudinal paper examining the links 
between time spent sitting and mortality in a sample of more than 17,000 
Canadians (available here). Not surprisingly, they report that time spent 
sitting was associated with increased risk of all-cause and cardiovascular 
disease mortality (there was no association between sitting and deaths due to 
cancer). But what is fascinating is that the relationship between sitting time 
and mortality was independent of physical activity levels. In fact, 
individuals who sat the most were roughly 50% more likely to die during 
the follow-up period than individuals who sat the least, even after controlling 
for age, smoking, and physical activity levels. Further analyses 
suggested that the relationship between sitting time and mortality was also 
independent of body weight. This suggests that all things being equal (body 
weight, physical activity levels, smoking, alcohol intake, age, and sex) the 
person who sits more is at a higher risk of death than the person who sits 
less.The above findings linking excessive sitting with poor health are far from 
isolated. For example, a similar longitudinal study from Australia reports that 
hour of daily television viewing (a proxy of sedentary time) is associated with 
an 11% increase in the risk of all-cause mortality regardless of age, sex, 
circumference, and physical activity level. And as my colleagues and I 
in a recent review paper (PDF), numerous epidemiological studies 
have linked sedentary behavior with obesity, cardiometabolic risk, and even 
cancers.New evidence also suggests that in addition to the quantity of 
time, the quality of sedentary time may also have an important health 
impact. For example, Genevieve Healy and colleagues examined this issue in 
participants of the Australian Diabetes, Obesity and Lifestyle (AusDiab) Study. 
total of 168 men and women aged 30-87 years wore an accelerometer (an objective 
measure of bodily movement) during all waking hours for 7 consecutive days, 
which allowed the researchers to quantify the amount of time that participants 
spent being sedentary, as well as how frequently they interrupted these 
sedentary activities (e.g. standing, walking to the washroom, etc).What did 
they find?The greater the number of breaks taken from sedentary behavior, the 
lower the waist circumference, body mass index, as well as blood lipids and 
glucose tolerance. This was true even if the total amount of sedentary 
time and physical activity time were equal between individuals—the one who took 
breaks more frequently during their time at the office or while watching 
television was less obese and had better metabolic health. Importantly, the 
breaks taken by the individuals in this study were of a brief duration (<5 
min) and a low intensity (such as walking to the washroom, or simply 
standing).Taken together, the epidemiological evidence strongly suggests that 
sitting is an important health risk factor. But what explains these 
relationships? Let’s now look at the multiple mechanisms linking sedentary time 
with increased health risk.MechanismsReduced Energy ExpenditureQuite obviously 
(and by definition), when you are sedentary, you are not 
being physically active. And so one common assumption is that people who sit 
more are at increased health risk simply because they are getting less physical 
activity. However, somewhat surprisingly, sitting time and physical activity do 
not appear to be related for most people. For example a paper from the European 
Youth Heart Study published in PLoS Medicine reports no association between 
activity and TV watching in a sample of nearly 2000 children and teenagers, and 
other reports suggest that there is little evidence that 
sedentary behavior displaces moderate or vigorous physical activity. So while 
makes intuitive sense that being sedentary reduces energy expenditure, it is 
likely through the reduction of very light intensity physical activity (e.g. 
standing, walking at a slow pace), rather than by reducing the volume of what 
typically think of as exercise. This may also help explain why the relationship 
between sedentary behavior and health risk are often independent of moderate or 
vigorous physical activity.Increased Food IntakeIn addition to reducing our 
energy expenditure, sedentary behaviors may also 
promote excess food intake. For example, a recently published study in the 
American Journal of Public Health suggests that the 
amount of commercial television (e.g. television with advertisements) that 
children watch before the age of 6 is associated with increased body weight 5 
years down the road, even after adjustment for other important variables 
including physical activity, socio-economic status and mother’s BMI. In 
contrast, watching non-commercial television (DVD’s or TV programs without 
commercials) showed no association with body weight. Similarly, it has also 
reported that each hour of daily television watching in children is associated 
with an increased consumption of 167 calories per day (PDF), mainly through 
increased consumption of high calorie, low nutrient foods (e.g. the foods most 
commonly advertised on television). Much of this is likely just a learned 
behavior—watching TV exposes us to food ads promoting unhealthy fare, which is 
likely to have a disproportionate influence on younger viewers. Just as 
importantly, people may just really enjoy munching on food while relaxing on 
couch. Either way, excess sitting (and TV watching in particular) seems to put 
us in situations where we choose to eat more than we would 
otherwise.Physiological AdaptationsI don’t think the mechanisms described 
above—that sitting too much may lead 
to reduced energy expenditure and increased food intake—will come as much of a 
surprise. But what I find truly fascinating is that sedentary behavior 
also results in rapid and dramatic changes in skeletal muscle. For 
example, in rat models, it has been shown that just 1 day of 
complete rest results in dramatic reductions in muscle triglyceride uptake, as 
well as reductions in HDL cholesterol (the good cholesterol). And in healthy 
human subjects, just 5 days of bed rest has been shown to result in increased 
plasma triglycerides and LDL cholesterol, as well as increased insulin 
resistance—all very bad things. And these weren’t small changes—triglyceride 
levels increased by 35%, and insulin resistance by 50%!These negative changes 
are likely related to reductions in the activity of 
lipoprotein lipase, an enzyme which allows muscle to uptake fat, thereby 
reducing the amount of fat circulating in the blood (it also strongly 
cholesterol levels—the details can be found here). Animal 
research has shown that lipoprotein lipase activity is reduced dramatically 
after just six hours of sedentary behavior—not unlike a typical day at work or 
school for many individuals. Sedentary behavior may also reduce glucose 
transporter protein content in the muscle, making it more difficult for glucose 
to be taken into the muscle and resulting in higher blood sugar levels. What is 
most interesting to me personally is that these physiological changes in 
skeletal muscle have little or nothing to do with the accumulation of body fat, 
and occur under extremely rapid time-frames. This means that both lean 
and obese individuals, and even those with otherwise active lifestyles, are at 
increased health risk when they spend excessive amounts of time sitting 
down.Should we be concerned about the health impact of sedentary 
behavior?Yes.Western society is built around sitting. We sit at work, we sit at 
school, we sit at home, and we sit in our cars as we commute back and 
forth. In fact, a recent 
survey reports that the average American accumulates more than 8 hours of 
sedentary behavior every day—roughly half of their waking hours. The situation 
in children is, unfortunately, no different. There is evidence that children in 
both Canada and the USA (PDF) 
accumulate more than 6 hours of screen-time (time spent in front of the TV, 
computer, or other screen-based device) on a daily basis. Keep in mind that 
screen-time is almost exclusively sedentary (active video games excluded), and 
that all these hours of sedentary behavior are in addition to the hours and 
hours (and hours) that kids spend sitting at school. In fact, a recent study 
reports that roughly 70% of class time, including 
physical education class, is completely sedentary (while slightly better than 
class time, children were also sedentary for the majority of lunch and 
recess).In short, given the consistent links between sedentary behavior and 
death and disease, and the ubiquity of sedentary behavior in our society, we 
should be very concerned about the health impact of sedentary behavior.What is 
the take-home message?There is a rapidly accumulating body of evidence which 
suggests that 
prolonged sitting is very bad for our health, even for lean and otherwise 
physically active individuals. The good news? Animal 
research suggests that simply walking at a leisurely pace may be enough to 
rapidly undo the metabolic damage associated with prolonged sitting, a finding 
which is supported by epidemiological work in humans. So, while there are a 
lot of questions that remain unanswered (e.g. Is there a “safe” amount 
of daily sedentary time?), the evidence seems clear that we should strive to 
limit the amount of time we spend sitting. And when we do have to sit for 
extended periods of time (which, let’s face it, is pretty much every single day 
for many of us) we should take short breaks whenever possible.Finally, if you 
take only one thing from this post, let it be this—sitting 
too much is not the same as exercising too little.





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