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Can sitting too much kill you?

The views expressed are those of the author and are not necessarily those of Scientific American.

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We all know that physical activity is important for good health—regardless of your age, gender or body weight, living an active lifestyle 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 50 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 perform 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 Evidence

In 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 each 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, waist circumference, and physical activity level. And as my colleagues and I summarize in a recent review paper (PDF), numerous epidemiological studies have linked sedentary behavior with obesity, cardiometabolic risk, and even some cancers.

New evidence also suggests that in addition to the quantity of sedentary 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. A 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 prolonged 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.


Reduced Energy Expenditure

Quite 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 physical 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 it 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 we 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 Intake

In 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 been 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 the 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 Adaptations

I 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 influences 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?


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 both 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.

Image Credit: Josh Semans, from Flickr.

About the author: Travis Saunders is a Certified Exercise Physiologist and PhD Candidate at the University of Ottawa in Ontario, Canada. His research focuses on the relationship between sedentary behavior and chronic disease risk in children. When he is not in the lab, he can be found blogging at Obesity Panacea and Science of Blogging, and running marathons with his fiancé. He can be reached at @travissaunders.


The views expressed are those of the author and are not necessarily those of Scientific American.


Comments 29 Comments

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  1. 1. EoRaptor 2:19 pm 01/6/2011

    Although I am a software engineer, I long ago developed the habit of standing while working. My keyboard, mouse, and monitor sit on the standard bookshelf that comes with most cubes. My question, however, given the formal definition of sedentary, am I actually helping myself?

    I do tend to pace while thinking… one and one-half step in one direction, one and one-half in the other. Also, if I want to get something, I just go; I don’t have to think about coming back, getting all comfortable again, etc. Nevertheless, I don’t think swaying from one foot to the other is what you had in mind.


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  2. 2. TravisSaunders 3:39 pm 01/6/2011

    Great question, and the short answer is that we don’t really know. But it seems that even minor increases in muscle motor activity is enough to prevent or reverse the metabolic adaptations observed in response to prolonged sitting. So it’s not certain, but it’s at least plausible that standing is healthier than sitting, and a lot of researchers in this area are advocating that when possible, people work while standing rather than sitting.

    For my part, I’ve started using a small pedal machine which fits under my desk, so that I can keep my legs moving while I type. Again, whether or not this makes a difference is unknown, but given that there are few or no side effects I’m willing to give it a shot.

    Now whether standing or using a small pedal machine puts someone above the 1.5 MET threshold and therefore puts them out of the "sedentary" zone, I’m not sure. But the physiology is what really matters, and the definition can always adapt as our understanding of the sedentary physiology improves.


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  3. 3. gburnett70 4:03 pm 01/6/2011

    Hello Travis,

    As a scientist and writer who sits for many hours a day, your article really hit home. I’m going to see about redesigning my workspace so I can stand, but in the meantime what pedal device do you use?

    Greg Burnett

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  4. 4. TravisSaunders 8:31 pm 01/6/2011

    Hi Greg,

    Thanks for the comment, I’m glad the article had a positive impact!

    This is the pedal machine that I use:–productId_10255247.html

    Ideally I’d love to have a treadmill work station, but unfortunately we just don’t have the space for one at the moment. The pedal machine isn’t perfect (I had to switch to a non-rolling chair, and if you’re not careful you can bang your knees on your desk from time to time), but I’m happy with it so far.

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  5. 5. vzeoe65i 8:40 pm 01/6/2011

    " an active lifestyle can improve your quality of life and dramatically reduce your risk of death and disease."

    An active lifestyle can reduce the risk of disease but not death. We are all
    mortal and death is a fact of life.


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  6. 6. Rhythman 12:24 am 01/7/2011

    It would seem that the simple act holding oneself in an upright position would cause a host of muscles to work in a constant flow just to fight gravities way of having us flat on the ground.
    Also, the heart/lung and maybe especially the Lymphatic system would seem to be much more active comparing the extremes of lying down or sitting to standing.

    I took to standing while working, and even at times while watching TV, after a bad back kept me from even thinking of sitting.
    It takes a little getting used to but then again we can take a break from it whenever we want, (unlike Sec. of Defense Rumsfeld’s false and cynical comparison of his standing-work habits to the forced holding-positions at Abu Ghraib and other ‘detention’ centers).

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  7. 7. jgrosay 7:30 am 01/7/2011

    Good article. It was know previously that sitting with your legs down for long periods, such as in a long distance flight can greatly increase your risk of deep venous thrombosis (DVT) and pulmonary embolism, both potentially lethal disorders. In some Mediterranean countries you can see old women sitting for hours in front of her homes, perhaps a suicidal act, and there is a sentence stating "Sit in the front of your home and you’ll see the corpse of your enemy pass by". May be you’ll be the next one to pass away

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  8. 8. TravisSaunders 10:00 am 01/7/2011


    I can’t disagree with you on the certainty of death – I meant "risk of death within a given time frame", which *is* lowered by an active lifestyle.


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  9. 9. openmedia 5:16 pm 01/7/2011

    So much for meditating for long stretches of time.

    Speaking of stretches, I wonder if stretching the body is mostly sedentary? Would reading/working while stretching (on the floor or standing) be much improvement over reading in an easy chair? I’d guess it is better but not a substitute for active breaks from reading.


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  10. 10. adamsn06 7:05 pm 01/7/2011

    So let me put on my skeptic’s hat … the implication here is that sedentary behavior (which is assumed to be a choice) causes higher cvd mortality … how would we design an experiment to show that the causation isn’t reversed? From the main study cited here I could conclude that poor cv health causes sedentary behavior, rather than the opposite.

    I personally speculate that more sitting may cause more back problems which somehow could lead to increased cvd mortality. But I don’t think there really anything here that establishes causation.

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  11. 11. Jculpepper 8:22 pm 01/7/2011

    It would seem more natural and healthier to squat, as they do in much of Asia.

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  12. 12. unfavorable_odds 9:07 am 01/8/2011

    Look, I advocate on behalf of the American Heart Association for increased physical activity at school, and I strongly believe that there is a correlation between improved learning and physical activity, and a whole host of other social and physical benefits. So reducing the amount of sitting is something I completely support.

    But I also support better controlled research than what is cited here. Most of it shows correlation, not causation.

    Here’s a generic example of correlation: a reduction in obesity rates is tied to income and education levels. So if I increase my education level, will I be thinner? Many people might say yes. But the increase in education level may simply be a symptom of someone having greater self-discipline to finish what they started. Which means self-discipline is what provides the cause, not education.

    This article definitely implies a correlation between sitting and life expectancy. But does it lead to causation? I’m not so sure.

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  13. 13. hereNT 7:59 pm 01/8/2011

    I wonder if using an exercise ball instead of an office chair for computer work time would make a difference? I kind of fell out of the habit but last summer I used one exclusively and my core stomach muscles ended up in the best shape of my life, without doing situps or anything else. Seems like it encourages small active movements, but I don’t know if it would be enough to get over the threshold for ‘sedentary’

    Can’t hurt, I’m putting my office chair off to the side and using the ball all the time again :) As a computer programmer who works from home I end up with a whole lot of ‘screen time’ every day.

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  14. 14. hsingichuan 2:49 am 01/9/2011

    I’ve taught T’ai-Chi since 1985 and I’ve noticed that in general, the less people move the less healthy they are. As I, and the entire country are spending more and more time on-line, I think it is more important than ever to break up periods of sitting with moderate exercise, stretching and fresh air. I know how it feels to be on a roll on-line and to feel like any break will somehow result in some kind of loss, but when I actually take a short break, even it it’s just to do the dishes are walk around our apartment, I feel much better. Sitting is not what we are adapted to do. We are adapted to do physical work. There are Traditional Chinese Medical reasons to avoid long periods of sitting too. Walk or bike to or from work, take a walk at lunch time, get up and stretch of a few minutes periodically, take up a game or sport that involves movement, all things that help keep your energy from stagnating and causing health problems. And you don’t need a study to tell you that. Try it and you’ll notice the difference. IMO. ;~)

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  15. 15. hsingichuan 2:49 am 01/9/2011
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  16. 16. TravisSaunders 12:20 pm 01/10/2011

    You are right that epi papers can’t conclusively prove causation. But the intervention studies that I describe in the "Physiological Adapatations" do suggest causality – make rats immobile for 6 hours, and their LPL activity drops by half, and at 18 hours it’s almost undetectable. Similarly, insulin sensitivity drops dramatically after just a few days of bed rest in humans, and cutting the nerve supply to skeletal muscle also results in rapid and dramatic changes. Similarly, the re-introduction of movement seems to return things back to normal.

    There is undoubtedly some reverse causality as well – unhealthy individuals may be more likely to become sedentary as a result of their condition, but the physiological studies in this area suggest to me that sedentary behavior itself plays an important role.

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  17. 17. TravisSaunders 12:22 pm 01/10/2011

    Good question. The issue seems to be one of muscle activation – e.g. the muscle needs to be actively contracting. So if that is true, I would think that stretching would only be useful if you were actively moving your limbs quite a bit – e.g. having someone passively stretch or massage your muscles probably wouldn’t work. That being said, I don’t know of any studies looking specifically at stretching, so I can’t really say with certainty.

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  18. 18. dvdccks 4:11 am 01/12/2011

    As a fire and safety inspector for insurance carriers I occasionally do ergonomic surveys of office workstations. One of the general suggestions I give the HR Manager is to provide a one liter water bottle to every employee with the instruction to drink one before lunch and one after lunch. The punch line is much sooner than later they will have to use the restroom. And they should take the long way to return and refill the bottle at the water cooler on the way back.

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  19. 19. CareerDiva 2:01 pm 01/12/2011

    Hey Travis: I really appreciate a scientific take like this on the topic of sitting too much. I recently embarked on a totally unscientific standing-desk experiment and found I was more productive and had less back ache. Who knew! I did a couple of YouTube videos about my experience. Here’s a line to one:

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  20. 20. bucketofsquid 5:12 pm 01/12/2011

    While technically incorrect, the way travis phrased it is common usage and generally understood to mean risk of death prematurely. There are a few longetivity researchers that believe that death isn’t a mandated biological function but is instead the result of outside influences such as disease, contamination or a fast moving bus. If they are correct then his useage would actually be technically correct but I don’t think they are.

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  21. 21. jsnaric 7:50 am 01/14/2011

    Tremendous article! It promted me to visit your blog Obesity Panacea, and I’m equally impressed with your content. I look forward to more. I have recently created a website to help with the obesity epidemic so I have a great amount of interest in what you write about. Thanks.
    Jay Snaric

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  22. 22. jsnaric 7:51 am 01/14/2011

    Tremendous article! It prompted me to visit your blog Obesity Panacea, and I’m equally impressed with your content. I look forward to more. I have recently created a website to help with the obesity epidemic, so I have a great amount of interest in what you write about. Thanks.
    Jay Snaric

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  23. 23. vrulg 10:10 pm 01/20/2011

    I recall reading about a study a few years ago that showed a health benefit from what one might call "nervous behaviors" e.g. toe taping, leg shaking, or just being unable to sit in one position for more than a few minutes at a time. I can’t find anything on the research now, but if I recall the researchers tried to explain this in terms of the slight increase in calories expended(something like 5 or 10 an hour?) that these behaviors had. It would be interesting to see that toe-tapping research re-done or re-interrupted in light of these sedentary findings.

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  24. 24. amylynn1022 10:38 am 01/21/2011

    On the one hand, I find this article hopeful, in that it suggests that getting any movement, even if it is of short duration and low-impact, can do some good. Too much of what I read about exercise seems to imply that if you are not in the gym at least an hour a day sweating then you may as well not bother. On the other hand, it points to what in some ways in an even bigger change in how we order our lives. While I enjoy reading about people adjusting their workstations so they can work while standing, the truth is a lot of us (including me, currently) do not have that kind of control over their work environments. How do we convince the employers of the world that making employees sit (or do anything repetitive) all day is counter-productive?

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  25. 25. gsegol 4:00 pm 01/21/2011

    I think the conclusions are erroneous. Sedentary is "any behavior with an exceedingly low energy expenditure"–in short, not moving. Consequently, "sitting too much" translates to "moving too little," and the conclusion is that moving too little and/or exercising too little are bad for you. No surprise. The 60-minutes per day quota is wrong. Keep moving.

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  26. 26. amylynn1022 1:13 pm 01/22/2011

    With respect, gsegol, I think you missed my point. (Or maybe I didn’t make it clear.) I agree with you definition of "sedentary" but as Travis Saunders pointed out the current guidelines used in his research and in education campaigns define "sedentary" as not meeting the physical activity requirements a "one hour a day of ‘exercise’" which is not just movement. I was adding an admittedly anecdotal observation that these physical activity guidelines are often presented in a way that makes it sound like if you are not "exercising"–which for most people brings up images of serious exertion–an hour a day you may as well be a couch potato. (I am not saying that I agree with this assumption I am saying that public health campaigns and popular media give this impression.) Saunder’s research would seem to point to the fact that regular movement throughout the day is important to overall health, whether or not you get enough "exercise".

    All of that is really a digress from the main point of my original comment. I was responding to a number of earlier comments about people who have modified their work environments. I pointed out that a lot of workers do not have that kind of control over their work spaces and asked for suggestions on encouraging employers to make this sort of regular movement possible. Even better, suggest that it might be in the employers best interest to do so. I am speaking as someone who is currently in a job where I not only have limited control of my workspace–I was in my current job a year before I even got an assigned workspace, instead of just having to grab whatever station was open when I came in–but also cannot just take a quick break to move away from my desk without potential penalty. This is the sort of culture–not uncommon, I fear–that contributes to sedentariness as much as TV watching or other screen time.

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  27. 27. davidpla 7:20 am 01/23/2011

    I have read somewhere recently that constant jiggling, fidgeting, foot tapping etc while sitting can use a surprising amount of energy/calories. I do this a lot. Any comment about this?

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  28. 28. MichelleJ 12:13 am 01/27/2011

    Hi Travis, I’ve been using a sit-stand desk for about a year. At first it just helped relieve back and hip tension throughout the day, but recently I’ve been reading more about these body moniters that show how many calories you can burn by standing more throughout the day. I work out 4x/wk, but find it hard to add in walking or other exercise in the winter. So I’ve been using standing as my secondary "workout." One guy at work lost 12pds just by standing more.:-) Anyway, here’s a site that brings more of the research together for people: Will get your resources added here too. Great info!


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  29. 29. u14010187 11:21 am 05/2/2014

    I tend to sit for hours straight watching TV. I didn’t realize how bad sitting for long was, until I did a bit of research. I gathered that prolonged sitting decreases circulation, and the body can start to shut down on a metabolic level. People have lipoprotein lipase enzyme, and when people sit for a long time this enzyme falls, this increases weight, and high blood sugar increases. Many health problems are associated with prolonged sitting it lowers the level of HDL cholesterol, and increased levels of triglycerides. Long periods of sitting can also result in muscle fatigue, aches, and injuries. When you sit for long muscles burn less fat and blood flows more sluggishly, allowing fatty acids to easily clog the heart. Prolonged sitting has been linked to high blood pressure and elevated cholesterol. People with the most sedentary time are more than twice as likely to have cardiovascular disease as those with the least. People should do regular exercises, have one to two minutes break of walking around during their long hours of sitting this will improve their health.

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