Modern life has given us many conveniences. With technology, we're able to send messages within seconds, commute with much less effort, and endlessly binge on our favourite shows from handheld devices. The result of this is that many of these advancements have habituated us into a lifestyle of inactivity. From work to enjoyment activities, the modern lifestyle is designed to make us move less.
Research conducted in 2016 shows that the average adult American is sitting an average of 6.5 hours a day — about an hour increase from the 2007 average.¹
For office-bound workers, this may increase to 10 hours. Global studies also indicate that 1 in 4 adults and three-quarters of adolescents do not meet recommended guidelines for aerobic activity.²
Unfortunately, moving less is not as benign as it seems and health experts are worried about what it's doing to our health.³ ⁴
Physical inactivity accounts for 6-10% of major lifestyle diseases like coronary heart disease, diabetes, and breast and colon cancers.
Comparisons of different occupations also show that bus drivers (who spend much of their time sitting) have twice the rate of cardiovascular disease compared to conductors (who spend more time walking).⁵
Such statistics may come as no surprise, as there are many public health campaigns surrounding lifestyle diseases.
However, more recent research from the US is painting an even more serious picture about the perils of sitting too much — it can increase your risk of dying. In 2008, it was estimated that physical inactivity was the cause of approximately 9% of yearly premature mortality (approximately 5.3 million deaths worldwide).⁶
And according to the World Health Organisation (WHO), it's also the 4th leading risk factor for death globally.⁷
It's estimated that if we can even reduce sedentary behaviour by 10% to 25%, about 500,000 to 1.3 million deaths can be prevented. And life expectancy may be increased by 0.68 years.⁸
But before you start planning a few extra 45-minute workout sessions after a whole day of sitting at the office, it's important to note that how we clock our active hours also matters. And experts are now suggesting that breaking up sitting time throughout the day is the key to reducing risk.
In the study that involved 7,985 participants over 45 years of age, those who were inactive for a total of more than 12.5 hours a day with sedentary bouts of more than 10 minutes were at the highest risk of mortality.⁹
When the researchers looked at sedentary bouts in isolation, clocking inactive periods within a 1-29 min period was associated with less death risk compared to 60-89 min and ≥90 min periods. But it should be noted that short inactive bouts with high total sedentary hours were still associated with increased mortality risk.
While this study had its limitations in the sense that all the participants were over 45 years of age, a study in Australia had similar findings. Even for the participants that were active for more than 300 minutes a week (more than double WHO recommendations), there was still a greater risk of death due to prolonged sitting.¹⁰
The key takeaway from all this research was that it's not only important to look at total sedentary time. The periods in which its accumulated matter too. This means concentrating exercise to one 30 minute block each day may not be enough to reverse the effects of sitting for the rest of that time.
Experts are aware that the downside to such information is that it can result in feelings of discouragement from people. But if we look on the bright side of this latest research, it actually means that making small, incremental movements throughout the days can make a big difference to overall health too.¹¹ For example, one study has found that breaking up long periods of sitting with 6-min high-intensity exercises can activate circulatory and metabolic responses in the body.¹²
So, how exactly does something as benign as sitting lead to these serious health effects? Here's what's happening to your body when it remains idle:
According to experts, changes in our body at a chemical level are the core of how inactivity affects our health. When we stop moving, the enzyme (called lipoprotein lipase (LPL)) responsible for breaking down fat in the bloodstream and controlling your level of "good" cholesterol becomes dormant.¹³ LPL disruption has been linked to hypertension, coronary artery disease, and more.¹⁴
Resistance to insulin (which helps your body convert the sugar from food into energy) has also been associated with lack of movement — a hallmark sign of type 2 diabetes. Conversely, studies have also shown that breaking up prolonged sitting with short bouts of walking can result in improved insulin responses across people from different racial backgrounds.¹⁵
Because these metabolic processes (converting food into energy) are reduced during sitting, it also means that we're burning less calories. And this is why inactivity is often related to obesity. It's estimated that people can use about 50 more calories in a six-hour period if they spend it standing rather than sitting.¹⁶
Researchers are also exploring a multitude of other genetic and chemical responses our bodies go through when remaining idle.¹⁷ ¹⁸ But taken together, a clear trend is emerging that shows how inactivity is stopping our body from performing as it should at the cellular level.
For most of us, the most apparent damage that sitting to our bodies usually comes in the form of muscle or skeletal pain — particularly in the back and neck. When we don't move, muscles all around our body relax and deactivate. Meaning, if you don't use it, you really do lose it.
This can lead to all sorts of issues like reduced hip extension, pressure on the spinal discs that lead to early degeneration, nerve damage, and loss of muscle mass.¹⁹ ²⁰ ²¹ ²²
These changes can result in debilitating chronic pain and stiffness that affect daily functioning. Because we're often working on computers while sitting, this can also lead to poor posture like hunching over or rounded shoulders.²³
Researchers have found that too much sitting impacts our brains and mental health as well — even though it's still much less studied.
In one recent study that examined the effect of prolonged sitting on blood flow to the brain, participants were assigned to 3 different conditions:
4 hours of sitting
4 hours of sitting with a 2-min treadmill walk every 30 minutes
4 hours of sitting with an 8-min treadmill walk every 2 hours
The researchers found that only conditions A and C resulted in a significant decrease in blood flow to the brain. But this was prevented in condition B. This shows that breaking up long periods of sitting can affect our brain health. The findings of this study are significant because having enough blood flow to the brain is essential for cognitive functioning while decreased levels have been associated with diseases like dementia.²⁴
Additionally, it also seems that our mental health can be impacted by inactivity. A long-term adolescent study tracked participants' activity level and mental health across the ages of 12, 14, 16, and 18 years of age. The researchers found that each additional hour of sitting as 12, 14, and 16 years old was linked to elevated depressive scores at 18 years old.²⁵
Similar findings have been reported in the workplace setting as well. In one Australian study involving 3,367 state government employees, participants that sat at work for more than 6 hours a day were more likely to report higher levels of moderate anxiety and depression symptoms compared to those who only sat for less than 3 hours a day.²⁶ Increased sitting time has also been associated with lower reported job satisfaction and higher exhaustion for office workers.²⁷
The latest studies on sitting also have implications for public health guidelines. Currently, the WHO only recommends at least 150 minutes of moderate-intensity physical activity a week. As of 2020, it also states that more research is still needed before it is able to provide a specific maximum limit to sedentary hours within a day.²⁸ ²⁹
However, in light of the latest research, some experts suggest that limiting any sitting period to less than 30 minutes is a good starting benchmark.³⁰ Other recommendations to office workers include having at least 2 hours of light activity (standing or walking) during working hours, and accumulating to 4 hours if possible.³¹
At a community level, doctors and health professionals may also need to start recommending that people limit sitting duration in addition to accumulating a total number of weekly active minutes. This would be similar to how the public has already been educated about limiting exposure to the sun or second-hand smoke.³²
With so many numbers and guidelines thrown around by different health authorities and researchers, understanding how much to move can be confusing.
To put it simply, most experts would recommend following the WHO guidelines (150 minutes of moderately intense physical activity per week) and reducing long periods of sitting — this means limiting to 30 minutes at a time.³³ ³⁴
There have been many suggestions around the simple lifestyle changes that can help people to achieve this:³⁵ ³⁶ ³⁷ ³⁸
Have walking instead of sit-down meetings
Opt for the stairs instead of the lift
Use commercial breaks during shows to walk around
Have adjustable sit-stand desks or workstations that allow you to mix up your position
Try doing daily cleaning or tidying more vigorously
Perform floor-based exercises after a period of sitting
Use apps to monitor your physical activity or set movement reminders
Walk while you're talking on the phone
Replace TV or screen time with a more active hobby
Stand in public transport
Walk over to speak to your colleague instead of sending an email
Experts emphasize that not all of these recommendations will suit everybody. But the point is to start making small changes to reduce sitting time during daily activities.
As Matthew Haines, Acting Head of Division for Sport, Exercise & Nutrition Science at The University of Huddersfield, has written in an article for The Conversation, "Ultimately, the most important thing is to avoid large chunks of sitting time. So, find out what works best for you and try and mix up your movement and activity every day — your body will thank you for it."
Health experts have figured out how much time you should sit each day | The Washington Post
Physical inactivity | World Health Organization
5 ways sitting is killing your nerves | Loma Linda University Health
Office workers, stand up from your desk for two hours a day | The Conversation
Why we should sit less | NHS
The author, Dawn Teh, is a health writer and former psychologist who enjoys exploring topics about the mind, body, and what helps humans thrive.