The study reveals that physically active individuals burn more calories over the course of the day and do not compensate by conserving energy in other bodily functions.
The University of Aberdeen, and Shenzhen University found that being active increases the total amount of energy the body uses each day without prompting it to cut back elsewhere.
While the health advantages of regular exercise are well established, scientists know less about how physical activity influences the body’s overall “energy budget,” meaning how energy is distributed among different biological processes.
For years, researchers have debated whether this energy budget works like a fixed income, where energy for movement is taken from other functions, or like a flexible system that expands to support more activity. The study aimed to identify which of these models best reflects how the human body manages energy at varying levels of physical activity.
To do this, researchers evaluated the total energy expenditure, or the total calories burned in a day, in participants across a wide spectrum of physical activity.
“Our study found that more physical activity is associated with higher calorie burn, regardless of body composition, and that this increase is not balanced out by the body reducing energy spent elsewhere,” said Kevin Davy, professor in the Department of Human Nutrition, Foods, and Exercise and the principal investigator of the study.
Participants were asked to drink isotopes of oxygen and hydrogen and then to have their urine samples collected over a period of two weeks. Oxygen is eliminated as water and carbon dioxide, and the hydrogen is eliminated only as water. The difference in the amount of each isotope lost is proportionate to the amount of carbon dioxide produced and, therefore, energy expended. Physical activity was measured using a small sensor worn at the waist that measures motion in multiple directions.
