The World Health Organization recommends 150 minutes of moderately intensive aerobic exercise per week. Most national health institutions advise a level of exercise within this same range. The fundamental question remains: does this recommendation stand up to the claim that this amount of physical exercise is sufficient for maintaining one’s physical and mental health? If you do the math, 150 minutes per week equates to a bit more than 20 minutes of exercise per day. Could such a short time frame be sufficient to counterweight the health hazards associating with sitting for 12 hours or more a day?
Recent evidence overwhelmingly suggests that this is not the case, and that even a more intense daily exercise regimen can simply not undo the unfavourable metabolic impact that results from being sedentary for the vast remainder of our waking hours.
Do We Really Sit That Much?
First off, do we really sit that much? You may be surprised to read these figures, but the time quickly adds up. The average office employee sits for around two-thirds of their work day, and those who sit the most at work also appear to sit more during transit, after work, and during weekends (Clemes et al., 2014). A French study involving 35,444 working adults with a mean age of 44.5, found similar patterns of behaviour. Working adults sat for an average of 12.15 hours on any given workday, and the more often they sat at work, the more likely they were to be sedentary outside of work (Saidj et al., 2015).
The Case Of The Active Coach Potato
Let’s consider the individual who does tend to sit a lot, but also regularly finds time for exercise. The term ‘active coach potato’ may not sound too charming, but it effectively sums up the lifestyle of the vast majority of those with office jobs. With so much time spent being sedentary in an office environment, you would think that people would be anxious to fill their leisure time with exercise and movement. However, the unfortunate reality is that sitting tends to yield more sitting. We live in a world with increasing professional demands, with many jobs demanding 50 hours or more of our time and attention each week. Not to mention the host of responsibilities and engagements most of us have outside of the office. This can make the idea of engaging in daily exercise seem like an unattainable illusion for many.
Exercise Doesn’t Compensate For All That Sitting
Let’s shed some further light on this topic. First off, we must determine whether exercise can counter the risks of a sedentary lifestyle, or rather, if extended periods of sitting constitute an independent risk factor, regardless of activity level. A recent scientific study, published in the 2013 Annals of Internal Medicine, investigated this very question (Biswas, et al. 2015). The authors conducted an impressive meta-analysis, distilling 47 previously performed studies, looking at all-cause mortality, cardiovascular disease mortality, cardiovascular disease incidence, cancer mortality, cancer incidence, and type 2 diabetes incidence in adults with the above described lifestyle (mainly passive, with short amounts of regular exercise). The conclusion was that prolonged sedentary time is independently associated with health risks, regardless of the amount of time an individual spends engaged in physical activity.
The results of this study constituted a paradigm shift within the scientific community which, with the help of supporting research, spread beyond academic circles and led to the rise of the popular headline comparing the risks of sitting with those of smoking. The comparison is a good one. If you are a smoker, you are still at risk to be diagnosed with lung cancer despite also being an active runner. By the same principle, if you maintain a sedentary lifestyle, there is still the same level of threat for heart disease, cancer, diabetes, overweight, dementia and many other chronic diseases, regardless of engaging in regular physical activity. Exercise cannot counter the negative effects of these dangerous habits. When evaluating one’s health, sitting time must be considered independently from time spent being active. With the exception of elite athletes who train vigorously for over 60–75 minutes at a time, the time you spend sitting each day cannot be reversed (Ekelund et al., 2017).
Let’s back that up with some more data. Activity patterns of more than 220,000 Australians 45 years and older were analysed in a 2012 study, published in Archives of Internal Medicine. The scientists linked prospective questionnaire data from people living in New South Wales and compared daily sitting time with all causes of mortality in that population. Measures were taken to ensure that variables such as sex, age, education, place of living, and smoking status did not falsify the data. The study concluded, once again, that the more hours spent sitting, the greater the chance of dying prematurely. Furthermore, research indicated that an individual’s risk didn’t change even if part of the day was spent exercising (Van der Ploeg et al., 2012).
While this has been proven repeatedly across a number of scientific studies, the reality has yet to enter the public awareness and therefore affect how we shape our professional and educational spaces. The widespread belief is that going for an evening run a couple of times per week puts you off the hook. If it were only so simple!
We Are Born Movers
In attempt to provide a better understanding and identify possible ways to alleviate this risk, we must consider the human body from both a macroscopic as well as a molecular level. Observations from the field of evolutionary biology hint where we can expect to find possible solutions. Our nomadic ancestors walked for most of the day and even our agrarian ancestors likely only sat for around three hours a day. When comparing against the grand scale of human existence on Earth, it is only in the past 150 years or so in which sedentariness rapidly became the unquestioned status quo. This period of time feels insignificant when considering the big picture in which the human genetic setup developed. Nevertheless, each cell in our body still contains the very same genetic code as our ancestors, which has prepared us for an entirely different status quo: that of an active mover.
Let’s dig into this a bit further. When we sit for a long time, muscle contractions — particularly in the legs — largely cease. The problem with this, contrary to popular belief, is not that our muscles are overall losing strength, but rather that the muscle contractions are not able to effectively serve their lesser known, second vital function. Our muscles are responsible for far more than moving a bone or a limb from position A to position B; in fact, they are an integral part of our whole cardiovascular system which, consisting of our heart and blood vessels, is in charge of transporting blood throughout our arteriovenous system. When our muscles don’t contract, immediately two things happen: first, they require less blood sugar to operate, and second, as pointed out above, blood begins to collect in the legs due to the force of gravity.
These two seemingly simple physical and physiological principles have huge implications which, in the same metabolic pathway, can end up increasing the effects of one another. Let’s consider this in greater detail.
With the musclular pump effectively being switched off, less blood makes its way through our body, including to the brain. The brain has a steady and permanent demand for energy in form of glucose, which is essential to ensuring that our body continues to function properly. As a consequence, our ancestral brain will always interpret reduced leg movement as a highly unnatural state, probably the result of an injury, such as an animal attack. In order to give us the best chance for survival in such a situation, the brain signals the body to increase the level of blood sugar and decrease the level of fat burning. As we discussed earlier, the brain enforces its survival needs through the release of hormones and gene regulation, all in favour of a single goal: to deliver energy to the brain in form of glucose as fast as possible. What had once been a basic physiological survival mechanism has now become a metabolic liability.
However, the problem of increased blood sugar is not solely caused by the top-down demands of the brain; it also results from a bottom-up principle of when the muscles are not moving. When not in need, our musculature naturally requires less energy. This results in a surplus of free fatty acids, which slows fat burning and creates an overall metabolic state that will only become more inflexible over the years. This will undoubtedly have far reaching effects and may set the stage for more ‘societal-based diseases.’
It is clear that simply no amount of exercise or level of fitness can change our body’s natural response in the described scenarios. Regardless of who we are, we have all been wired in the same way; each of our brains will interpret prolonged sitting simply as inactivity of large muscle groups combined with an unnatural posture. While serious athletes do have a different basic metabolic rate (BMR), meaning that, even when resting, the muscles that have been conditioned to be in regular heavy use will handle caloric intake in a different way than a less active individual. However, even this difference doesn’t cut the edge and still renders highly trained individuals almost as likely to be affected by the health hazards of sitting as untrained individuals.
We Overestimate Our Workouts
Furthermore, the effect of exercise on overall energy expenditure and impact of net daily sitting time has likely been overestimated. In Finland, a nation well-known for their wearable tracking devices, researchers employed a study in which active participants wore shorts designed with electrodes to measure the electric activity in the large leg muscles. The participants wore these trackers continuously over a number of days, regardless of whether they engaged in exercise or not. The study revealed two interesting facts. First, the amount of time spent exercising had no effect on the time spent in a sedentary posture for the remainder of the day. And second, the increase in energy expenditure on workout days was relatively small, averaging only 13% of the median increase on exercise days. It is clear that such a low margin would not suffice to have an impact large enough to influence the overall metabolism of one’s body.
Having such data available demonstrates that even daily exercise simply cannot result in a change profound enough to alter the basic way that humans breakdown nutrients, such as triglycerides.
17.000 Steps Per Day Made The Difference
This very question was addressed in a study at the University of Texas at Austin. The participants resembled the classic active couch potato lifestyle. The healthy young men took part in three five-day trials. In the first trial, the men sat for more than 14 hours per day and took in more calories than they were able to burn. The second five-day period took place after a waiting period of more than week, in order to minimise any potential residual effects. In this trial, the men also had to spend over 14 hours of their days being sedentary, but their calorie intake matched the energy they were burning. In the final five-day trail, the men had to walk for around 17,000 steps per day. In each of the three different trial settings, the participants ate a high-fat breakfast on the third and fifth morning, respectively. Also on these days, the subjects ran on a treadmill for one hour with high intensity.
The aim of the study was to look how each pattern of sitting influenced the way the body handles a fatty meal by measuring the free fatty acids floating in the blood after consuming a high-caloric breakfast. The main takeaway was that the body handles fat intake irrespective of exercise, and that prolonged sitting for 2–4 days in a row can lead to an unfavourable increase of fat levels, which in the long run can give rise to arterial diseases, such as atherosclerosis.
On the other hand, when the men had to walk for 17,000 steps throughout the day, their bodies were able to break down the fat that was leftover in their bloodstreams — specifically the bad kind of fat that can lead to the development of cardiac disease. This emphasises the much greater role of having an active lifestyle with lots of movement throughout the entire day, as opposed to trying to counterbalance too much time spent sitting with short, intense bursts of exercise (Kim, Il-Young, et al., 2016).
So what can we take away from all of this? We should look at exercise time and sedentary time as two entirely different entities. They are not as interconnected as we used to believe. Previously, public health programs and policies have primarily focused on the promotion of physical activity. This is probably misguided and doesn’t reflect the most recent scientific findings. In light of risks that have been associated with a sedentary lifestyle, we need initiatives whose primary goal is to limit sitting time. However, such guidelines will only be effective if people are given the chance to put them into practice. Overarching environments, such as schools and offices, must be reorganised in a way that acknowledges our need to move. A wide spread restructuring in this regard, including the private and public sector, seems far away and will undoubtedly face considerable challenges. To be successful, we must change the old view that productive and meaningful work can only be achieved by an employee in front of a computer screen, seated at his or her desk.