A major new study has found that physical activity boosts energy consumption throughout the day, not just when you are exercising, thus providing greater health benefits than previously thought.
Researchers have found that increased physical activity raises total energy use without triggering the body to conserve energy.
Basic functions keep running at full speed, even as movement increases: there is no compensatory effect elsewhere in the body that offsets exercise.
For years there has been a theory that when you are exercising vigorously, other functions in the body are throttled back in response, thus depriving you of some of the physical activity benefits.
Not so, according to the international team led by scientists at Virginia Tech working with colleagues from the University of Aberdeen and Shenzhen University. The study is published in the Proceedings of the National Academy of Sciences.
To resolve the question, the team measured total energy expenditure, meaning the total number of kilojoules burned in a day, among people with widely varying levels of physical activity.
"Our study found that more physical activity is associated with higher kilojoule burn, regardless of body composition, and that this increase is not balanced out by the body reducing energy spent elsewhere," said Kevin Davy, Professor of Human Nutrition, Foods and Exercise and the principal investigator of the study.
Participants’ physical activity levels varied widely, from sedentary to ultra-endurance running. There were 75 participants between the ages of 19 and 63.
Instead of saving energy in one area to make up for the calories burned through physical activity, the study found that the body continues to function at its usual rate, which means that overall energy use rises in direct response to increased movement.
For example, when the body is maintaining basic functions such as breathing, circulating blood and regulating temperature, the amount of energy it uses remains stable. This means the body doesn’t obviously compensate or 'cancel out' the extra calories burned through activity.
The research also found a clear link between being more active and spending less time sitting still. In simple terms, people who are more physically active are less likely to spend long periods of time being inactive.
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