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Sitting for more than six hours a day can affect metabolism, increase risks related to insulin, glucose, and circulation, and experts point out that short breaks of just two minutes every 20 or 30 minutes already help reduce some of these impacts on the body
Regular physical activity improves mental well-being, reduces the chances of developing diseases, and can increase life expectancy. Even so, the habit of sitting for long periods remains linked to significant health risks, especially when combined with physical inactivity.
The World Health Organization recommends that adults get at least 150 minutes of moderate activity per week, or 75 minutes of vigorous activity, in addition to two strengthening sessions. Still, only 73% of adults worldwide meet these guidelines, while 51% of Canadian adults are considered physically inactive.
What physical inactivity really means
Physical inactivity is defined as not meeting the minimum guidelines for a person to be considered active. This does not mean a total absence of movement, as someone can walk or do household chores and still not reach moderate or vigorous levels of activity.
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In general, physically inactive people also spend more time in sedentary activities. These activities involve little to no movement and include sitting, lying down, and standing, although for most people, the majority of sedentary time is spent sitting.
Several studies indicate that adults spend, on average, six hours a day sitting, but these results were obtained based on personal reports. The few studies that used direct measures of activity, such as accelerometers, indicate that this total may be closer to 10 hours daily.
This situation is concerning because the WHO classifies sedentary behavior as the fourth leading modifiable risk factor for death. The estimate presented is that with a 10% increase in physical activity, 500 million premature deaths could be avoided.
How the body reacts to sitting
From a biological perspective, being inactive is not just the opposite of being active. Sedentary activities cause their own physiological changes, and one of the main changes occurs in metabolism, which slows down when a person sits.
The logic is simple: when sitting, the body needs less energy. The comparison made is with a car engine that idles when stopped at a traffic light, reducing its operation when there is no need for greater effort.
Consequently, long periods of sitting can lead to the accumulation of triglycerides in the blood. As the body demands less energy in this position, enzyme production also decreases, including lipoprotein lipase, responsible for breaking down fats in the blood for muscles and organs to use as an energy source.
Studies with rodents showed a drop in the levels of this enzyme when the animals remained inactive. Over months and years, excess fat can impair insulin and glucose metabolism, which increases the risk of type 2 diabetes.
Sedentary behavior is also associated with muscle weakening, as muscles need movement to stay strong. When they are not used frequently, they shrink and progressively lose strength.
Furthermore, prolonged sitting can favor the continuous accumulation of blood in the legs, leading to problems such as varicose veins and deep vein thrombosis. Over the years, it also increases the risk of dementia, cancer, heart disease, and premature death.
Physical activity helps, but doesn’t eliminate all risk
The question of whether being active can compensate for time spent sitting is common, and the answer presented is yes, in general terms, being active even when spending long periods sitting is better than not being active. Still, this effect depends on the level of physical activity and the amount of time a person spends sitting.
In a study cited by the researcher, increased sitting time was associated with premature death regardless of the level of physical activity. The risk, however, was higher among less active people, showing that the two factors are cumulative.
Among those who met WHO guidelines, sitting for more than six hours a day presented the same risk as those who sat for less than six hours but did not meet the minimum physical activity recommendations. The result reinforces that both exercise and reducing sedentary behavior matter.
Sitting for less time consecutively is the best solution
Completely eliminating the habit of sitting is not considered necessary, nor desirable. Sitting remains important for rest, recovery, and more comfortable performance of many tasks, and today there is no specific target for total sitting time beyond the recommendation to reduce this period.
Standing is often remembered as an alternative, and the market for standing desks has grown in recent years. However, standing for too long produces a similar effect on metabolism as sitting, in addition to being linked to muscle fatigue, varicose veins, and a possible increased risk of heart disease.
The best solution suggested is to replace part of the time spent sitting, or even standing, with movement.
The cited study found a 2% reduction in the risk of premature death among people who sat for more than four hours a day when 30 minutes of that period were replaced by movement.
As it’s not always possible to set aside half an hour for this in all situations, the guidance is to reduce continuous and uninterrupted time in the chair. Interrupting sitting periods every 20 or 30 minutes with two minutes of activity, such as light walking, jumping jacks, squats, or other movement, is already enough to keep metabolism active and help control insulin and glucose.
To make this change a routine, the recommendation is to use a phone alarm to remember the break. Other alternatives include taking phone calls while walking around the office and holding walking meetings, simple strategies to break up long periods of sitting.
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