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Sedentary behaviour

Sedentary behaviour refers to activities that need very little physical movement and don’t use much energy, such as sitting or lying down for long periods of time. It is often called “too much sitting.” Sedentary behaviour is different from not getting enough exercise.

Researchers recognize sedentary behaviour as a health risk. Sedentary behaviour contributes to weight gain and becoming overweight or obese. It is associated with health problems including:

  • diabetes
  • heart disease
  • metabolic syndrome
    • Metabolic syndrome is a group of factors that put someone at risk for heart disease and diabetes. These risk factors include high blood pressure, high blood sugar levels, large waist size and abnormal cholesterol and triglyceride levels.
  • cancer

Measuring sedentary behaviour

Sedentary behaviour may be measured in different ways.

  • It is often measured by self-reporting, where people report the amount of time they spend sitting while watching TV or at work.
  • A device called an inclinometer can distinguish between sitting and standing.
  • It is also possible to measure sedentary behaviour with special devices called accelerometers. These devices measure the amount, frequency and intensity of movement. They may be used to measure time spent being active or inactive.
  • Metabolic equivalent (MET) is a measure of exercise intensity based on the amount of oxygen a person consumes. Generally, 1.5 METs or less is classified as sedentary behaviour.

The SITT formula may be used to describe the frequency, interruptions, time and type of sedentary activity.

  • S – sedentary behaviour frequency (the number of bouts of certain duration, or how often a person is inactive for a certain amount of time)
  • I – interruptions or breaks in sedentary time (such as getting up from the couch while watching TV)
  • T – time (duration of sitting)
  • T – type (type of sedentary behaviour, such as watching TV, driving a car or using a computer)

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Causes

Canadian adults are sedentary for most of their waking hours. For men, 68% of their waking hours are sedentary. Women spend 69% of their waking hours in sedentary activities.

Many Canadians spend a lot of their leisure time in sedentary activities. People are spending more and more time watching TV, using a computer, watching videos and playing online or video games. These screen-based forms of entertainment are examples of activities that usually involve a lot of sitting. Prolonged sitting also occurs with increased time spent in automobiles and sitting in the workplace (occupational sitting).

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Sedentary behaviour and cancer

A growing body of evidence supports a link between sedentary behaviour and an increased risk for cancer. The health risk from sedentary behaviour is not influenced by the amount of physical activity a person does, so it is an independent risk factor. Sitting for long periods of time can increase cancer risk, even in people who exercise regularly. Even if you exercise for 30 minutes or more a day, but spend the rest of the day in sedentary activities, you can still be at an increased risk for cancer. It is likely that the longer a person sits, the higher the risk. Research suggests that sitting for long periods of time uniquely affects certain body functions. Sedentary behaviour can cause the following cell and metabolic changes, which may contribute to cancer developing:

  • increased weight gain that leads to being overweight or obese
    • Being overweight or obese has been linked to several cancers.
  • changes in sex hormone levels
    • Increased androgen levels in men and increased estrogen levels in women are linked to hormone-related cancers, such as prostate cancer and breast cancer.
    • Sex hormone binding globulin (SHBG) binds to sex hormones and inactivates them. Decreased levels of SHBG may affect cancer risk. Physical activity increases SHBG levels, whereas inactivity decreases SHBG levels.
  • higher blood sugar (glucose) levels, increased insulin levels and insulin resistance
    • Cancer cells use glucose to grow and multiply, so increased blood sugar levels may promote cancer cell growth.
    • High insulin levels may increase insulin-like growth factor, which is involved in cell differentiation, growth and programmed cell death (apoptosis).
    • Insulin resistance may also promote the development of cancer in complex ways.
  • chronic inflammation
    • Chronic inflammation is associated with some types of cancer. Certain inflammation-type factors, such as tumour necrosis factor, interleukin-6 and C-reactive protein, are increased in chronic inflammation. Lower levels of anti-inflammatory factors may indicate a higher cancer risk.
  • decreased vitamin D levels
    • Some studies suggest that low vitamin D levels may increase the risk of some types of cancer.

Higher amounts of sedentary behaviour are associated with an increased risk of colorectal cancer.

There is some research that suggests work that is sedentary (occupational sitting) is linked to uterine (endometrial) cancer,  but the evidence is limited and more research is needed to confirm this.

The evidence around the effect of sedentary behaviour on cancer risk is new and still emerging. Further study is needed to clarify the role of sedentary behaviour for different types of cancers and identify effective ways to reduce sitting time.

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Sedentary behaviour in children

Research shows that Canadian children and youth spend the majority of their leisure time in sedentary activities.

Most of the evidence on the effect of sedentary behaviour on cancer risk comes from studies done on adults. Studies on the health risks of sedentary behaviour in children and youth have mainly looked at weight or body mass index (BMI), fitness, metabolic syndrome, school performance and other psychosocial effects. Researchers are studying whether sedentary behaviour during childhood and adolescence is a predictor of being overweight or obese during adulthood.

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Reducing your risk

Studies suggest that moving more to decrease the amount of time you spend sitting may help reduce your risk of cancer and improve your overall health. Tips to help reduce sitting time include:

  • Take frequent, short breaks from sitting. Breaks as short as standing or moving for 2–3 minutes can be beneficial. Even simple muscle movement has a beneficial effect on cell processes.
  • Walk around while you are talking on the phone.
  • Stand, rather than sit, on the sidelines while watching recreational games.
  • Take regular desk breaks to reduce sitting time while you are at work.
    • Walk to a central office waste basket or recycle container.
    • Take standing breaks during meetings.
    • Use a standing desk, if one is available, or sit on a therapy ball instead of an office chair.
  • Limit the amount of recreational time you spend watching TV or videos and playing on a computer.

In general, everyone should follow the guidelines for physical activity for their age group and limit time spent in sedentary behaviours. Being active has many health benefits, including reducing the risk of certain cancers.

In 2011, Canada released sedentary behaviour guidelines for early years, children and youth. For more information on the Canadian Sedentary Behaviour Guidelines, go to the Canadian Society for Exercise Physiology.

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