Regular physical activity is not only about fitness. It is a key factor for mental well-being, reducing disease risk, and increasing life expectancy.

According to recommendations by the World Health Organization, adults should get at least 150 minutes of moderate-intensity exercise per week—such as brisk walking or light cycling—or 75 minutes of vigorous activity, such as running or tennis. In addition, at least two strength-training sessions per week are recommended.

However, reality falls short of these guidelines: only 73% of adults worldwide follow them, while in countries like Canada, more than half of adults are considered physically inactive.

Scott Lear, a professor of Health Sciences at Simon Fraser University, explains in an article in The Conversation what physical inactivity does to the body and how we can incorporate more movement into daily life.

What does “physical inactivity” mean?

Physical inactivity is defined as not reaching the minimum levels of exercise recommended by experts. This doesn’t necessarily mean zero movement—many people may walk or do household chores but still not reach moderate or vigorous activity levels.

A key feature of physically inactive individuals is that they spend much of the day sitting. “Studies show adults report sitting about 6 hours a day, but objective measurements (e.g. accelerometers) suggest it can reach 10 hours daily,” notes the professor.

This is particularly dangerous, as physical inactivity has been identified by the WHO as the fourth leading modifiable risk factor for premature death. It is estimated that a 10% increase in physical activity could prevent up to 500 million premature deaths worldwide.

How does a sedentary lifestyle harm us?

Biologically, prolonged sitting is not just the opposite of exercise—it causes specific changes in the body. “When you sit, your metabolism slows down. This makes sense, as your energy needs are much lower—similar to a car engine idling at a traffic light,” he explains.

It can also increase triglyceride levels in the blood. “When sitting, the body produces less of certain enzymes, such as lipoprotein lipase (LPL), which helps break down fats so muscles and organs can use them for energy.”

With prolonged inactivity, increased fat levels can disrupt insulin and glucose metabolism, raising the risk of Type 2 diabetes.

Other risks include muscle weakening—since muscles need movement to stay strong—as well as varicose veins and venous thrombosis due to blood pooling in the lower limbs. Over time, the risk of dementia, cancer, heart disease, and premature death also increases.

Can exercise “offset” too much sitting?

A common question is whether exercise can cancel out the negative effects of prolonged sitting. The answer is partly yes: physical activity is clearly better than total inactivity, even if you sit for long hours. However, the level of protection depends on how much you move versus how much you sit.

Research shows that long sitting hours are linked to higher risk of premature death regardless of exercise levels—though the risk is greater for those who are not sufficiently active.

For example, people who meet WHO exercise guidelines but sit more than 6 hours a day may have a similar risk to those who sit less but do not exercise enough.

What can we do?

The goal is not to eliminate sitting completely, but to reduce it. Standing is often suggested as an alternative, but prolonged standing can also cause fatigue, varicose veins, and cardiovascular strain.

The most effective strategy is to integrate movement throughout the day.

Simple but meaningful changes include:

• Replacing 30 minutes of sitting with movement, which can reduce premature death risk by about 2%
• Breaking up sitting every 20–30 minutes with 2 minutes of light activity (walking, stretching, squats)
• Walking during phone calls
• Holding “walking meetings”

“While most people know that exercise benefits health, it is equally important to understand that sedentary behavior carries risks. Physical inactivity can negatively affect your health,” the professor concludes.