Why is sitting bad for you?
It is not only sitting, but inactivity (sedentary behaviour) in general that is bad for you. Until about 200 years ago, people were not inactive for more than 5 hours a day (excluding sleeping), and most periods of inactivity were broken up relatively often with movement. These days, our work environment, how we spend leisure time (watching TV, spending time on the computer or phone) and how we travel, can lead to some of us remaining inactive for up to 15 hours a day.
This lack of movement is one of the main reasons that so many chronic diseases have become more common. Physical inactivity is bad for us – surprisingly even for our brains – resulting in reduced muscle mass and strength, metabolic problems, and lower fitness. In fact, some reports suggest that sitting could be killing even more people than smoking. Specifically, sedentary behaviour, including sitting and TV watching, has been associated with increased all-cause mortality, reduced heath in general, and over 35 chronic diseases and conditions.
What counts as a sedentary lifestyle?
Inactivity is defined as any activity where we our metabolic rate is less than 1.5 times of that when we are resting and we are in a sitting or reclining position. Light physical activity, classified as strolling, cleaning the house, or cooking food, does not fall under this definition. In general, inactivity while standing, or even squatting, does not seem to be as detrimental – most likely due to the fact that major muscle groups are still active. In order to be sedentary, you need to be inactive for long periods of time – typically over an hour. In order to be classified as living a sedentary lifestyle, these bouts of inactivity need to add up to more than 6 hours a day – the point where studies have suggested that a significant risk for disease begins developing.
What happens when I’m inactive?
It is important to note that all of the following are independent of the amount of exercise you get, and therefore you might be at risk even if you exercise regularly. When you are sedentary, your muscles, especially the big ones in the lower part of your body, bear less weight and experience abnormal activation patterns. This leads to stress and strain on the back, neck and shoulders, as well as less blood flow to muscles. In addition to strain, your muscles switch off, decreasing your metabolic rate, and leading to metabolic changes, such as decreased sugar and fat metabolism.
These changes resulting from inactivity set in rapidly, and even a day of inactivity can reduce insulin sensitivity by 39%. Immediately after becoming sedentary, calorie burning processes slow down to about 1 calorie per minute (5% above basal energy expenditure). After an hour inactivity, enzymes involved in fat and glucose metabolism lose activity, resulting in fat deposition instead of metabolism. Within a week of adopting a sedentary lifestyle, LDL cholesterol and triglycerides begin to rise. Within two weeks of sitting muscle degeneration begins to set in, even if you work out. After a year of inactivity (while still exercising), effects such as weight gain, bone degeneration and high cholesterol, become noticeable.
What specific diseases are caused by a sedentary lifestyle?
A sedentary lifestyle has been associated with at least 35 chronic diseases, many of which you will recognise as being caused by other unhealthy habits imposed through our modern lifestyles. Prolonged inactivity has also been linked to chronic and increased inflammation, which can lead to numerous diseases, including those following, and has been heavily linked to metabolic syndrome (MetS).
Metabolic syndrome (MetS)
Metabolic syndrome has been widely associated with inactivity, as sedentary behaviour results in widespread changes in metabolism. Indeed, each extra hour of sitting may be associated with up to 19% increased risk of developing type II diabetes, and if you are inactive for most of your day, your risk of developing metabolic syndrome may be as much as 75% higher than if you weren’t.
Inactivity leads to worsened blood glucose management and insulin resistance. This happens rapidly after becoming sedentary, and insulin resistance has been one of the most significant conditions related to inactivity. In fact, people who sit the most have double the risk of developing type II diabetes, and a gain an additional 10% for each hour of inactivity.
Obesity or weight gain is most likely linked to a sedentary lifestyle for two main reasons. Firstly, due to less energy use and metabolic changes, and secondly, due to habits that are often associated with sedentary pursuits, such as snacking while watching TV. Not only is fat storage increased while sedentary, but its deposition is also altered. Most of this fat is deposited around the organs, such as the heart and liver, or is abdominal, which is extremely dangerous and further leads to MetS and other health issues.
Cardiovascular disease is one of the most well supported disease areas associated with prolonged inactivity. Indeed, the risk of cardiovascular mortality increases by at least 5% for each two hours of sitting time, and some reports state that people who sit the most are twice as likely to develop cardiovascular disease.
Specific conditions associated with sedentary time include heart attack, increased blood pressure, pulmonary embolism and deep vein thrombosis, venous thromboembolism, as well as increased cholesterol and triglyceride levels.
A number of cancers have been associated with inactivity, including colorectal, breast, endometrial, ovary, and prostate cancer. Research suggests that inactivity for at least 7 hours a day may result in at least 13% likelihood of dying from cancer. A main determining factor may be weight gain, leading to insulin resistance, chronic inflammation and hormonal disruptions, all of which are known to lead to cancer.
Impaired mental health
While research is still unclear in some cases, a sedentary lifestyle has been associated with a number of mental conditions. It has been reported that the risk for developing a mental disorder is increased by up to 31% in adults who watch more than 6 hours of TV per day compared to those who watch less than one and a half hours. This is likely due to both physical factors and psychological factors. Physical activity stimulates numerous biological pathways linked to mental function, maintenance and growth of neurons, reduced inflammation, release of mood modulating chemicals, and is often associated with better mental stimulation). Psychological factors related to inactivity, especially in terms of leisure time pursuits, include impaired social relationships and isolation in general. Of course, in this context, the type of sedentary behaviour is important, and activities, such as reading, playing board games, and crafts, that stimulate mental function are encouraged, especially in the elderly.
Specific conditions which have some evidence of being linked to a sedentary lifestyle include depression, anxiety, reduced academic performance and IQ, impaired memory and concentration, poor social performance, and low self-esteem. Sedentary behaviour has also been linked to worse mental aging (of up to 43%).
Our bodies are not designed to spend long periods of time in a sitting posture, and only use as much energy as is needed. Prolonged inactivity can therefore result in unusual neck and back curvature, back pain, neck and shoulder pain, and other issues such as carpel tunnel syndrome, muscle degeneration and osteoporosis.
Reduced sleep quality
Poor sleep patterns and quality are associated with many detrimental health impacts, including metabolic syndrome, cardiovascular disease, and poor mental health. Increased inactivity has in turn been associated with poor sleep quality, duration, frequent waking and apnoea, further adding to the risk of a sedentary lifestyle.
Will doing exercise help?
Exercise can result in improvements in many areas of health, but it appears that many bodily changes during inactivity are independent of the level of exercise – so even if you work out every day, sitting for the rest of it can put you at higher risk of developing this range of diseases
How can I reduce my risk?
The best way is to move as much as possible. Even a minor improvement is better than nothing, so stand up, walk, move your limbs, and change posture as often as possible. Breaks as short as a few minutes every hour can lead to a major improvement in the body’s metabolism and risk reduction, not only improving your health, but also your comfort, work performance, and concentration
It is suggested that at least 2 to 4 cumulative hours of light activity in place of sitting should remove most of the risk associated with a sedentary lifestyle. This would be best implemented as breaks of a few minutes every half an hour, where light to moderate activity is undertaken, although even just standing up can help.
Although standing can help to reduce the effect of inactivity, don’t overdo it. Movement is more important. Standing still for too long can result in discomfort, and a number of cardiovascular disease risks. The most important rule to remember is “everything in moderation”, extremes are bad.
Some simple suggestions to become more active include:
- Stand up and do something whenever your job or leisure time allows it – while eating lunch or taking a phone call, during the advertisements on TV, while your game is loading, take walking meetings, or walk to your colleague’s office instead of emailing.
- Some people might like to use a standing desk, with a highchair to sit at for brief periods when you become tired.
- Park further away from the office or mall, or use the bathroom on the next floor.
- Use the stairs whenever you can.
- Move your limbs around while sitting.