Sedentary behavior can raise the risk of heart disease, diabetes, and other conditions, even among people who are physically active. This is according to a new scientific statement from the American Heart Association.

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Sitting too much is detrimental to health, regardless of physical activity levels, say researchers.

In recent years, there has been an increasing number of studies documenting the harms of sedentary behavior - defined as any waking activity that involves sitting or lying down, such as watching TV or working on the computer.

Research has repeatedly linked sedentary behavior with increased risk of obesity, cardiovascular diseases, diabetes, and more.

A study published in the American Journal of Preventive Medicine earlier this year estimated that prolonged sitting is responsible for 430,000 all-cause deaths over 54 countries, and a more recent study claimed that sedentary behavior is a leading risk factor for mortality, second only to smoking.

While some studies suggest that physical activity can offset the harms of the prolonged sitting, other research claims that is not the case.

The new statement from the American Heart Association (AHA) - published in the journal Circulation - supports the latter, finding that no matter how much exercise one does, sitting too much is detrimental to health.

'Sit less, move more'

Deborah Rohm Young, Ph.D., chair of the AHA statement and director of behavioral research at Kaiser Permanente Southern California, and colleagues reached their findings after conducting a review of the current evidence on sedentary behavior.

Highlighting the fact that Americans spend too long sitting, the review revealed that younger adults in the United States are sedentary for around 6-8 hours a day, while adults aged 60 and older spend around 8.6-9.6 hours a day sedentary.

The authors explain that sedentary behaviors normally have an energy expenditure of 1.5 metabolic equivalents (METs) or less. Slow, leisurely walking or light housework uses around 2.5 METs, while vigorous to moderate physical activity uses around 3 METs or more.

Based on current evidence, Young and colleagues found that spending too much time sitting may raise the risk of impaired insulin sensitivity, diabetes, cardiovascular disease, and all-cause death.

What is more, the review revealed that these risks are not reduced by moderate to vigorous physical activity, suggesting that prolonged sitting is harmful to health, regardless of how much one exercises.

Young says that, at present, they are unable to pinpoint exactly how long is too long when it comes to sitting, but for now, their advice is to reduce the amount of time spent sedentary and increase the amount of time spent active.

"There's a lot of research that we need to do. This statement is important because it starts the ball rolling and suggests sedentary behavior may play an important role in heart health and more.

But, it's too early to make conclusive recommendations other than to encourage Americans to 'sit less, move more.'"

Deborah Rohm Young, Ph.D.

In line with the AHA's physical activity guidelines, the authors recommend engaging in around 30 minutes of moderate to vigorous physical activity daily; they note that exercising in smaller amounts each day is more beneficial than trying to fit in the same amount of exercise in fewer days.

Learn how prolonged sitting can worsen health for patients with heart disease.