Physical activity continues to affect the body even after the movement itself has ended.
A new study published in the Proceedings of the National Academy of Sciences reports that being physically active increases the total amount of energy a person uses each day. The research, led by scientists at Virginia Tech working with colleagues from the University of Aberdeen and Shenzhen University, found that this increase happens without the body cutting back energy use in other areas.
The finding matters because while the health benefits of exercise are well established, scientists know less about how physical activity influences a person’s overall “energy budget,” which refers to how energy is divided among the body’s many functions.
How the Body Manages Energy
For years, researchers have debated whether the body treats energy like a fixed paycheck or a flexible bonus system. One idea suggests that when people move more, the body shifts energy away from other tasks to pay for that activity. The other model proposes that energy use can expand, allowing total daily expenditure to rise as activity increases. The researchers set out to learn which of these ideas best reflects what actually happens across different activity levels.
To answer that question, the team measured total energy expenditure, meaning the total number of calories burned in a day, among people with widely varying levels 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.
Measuring Calories Burned in Real Life
Participants drank special forms of oxygen and hydrogen and provided urine samples over a two-week period. Oxygen leaves the body as both water and carbon dioxide, while hydrogen exits only as water. By comparing how much of each isotope was lost, researchers could estimate how much carbon dioxide participants produced and, in turn, how much energy they used. Physical activity was tracked using a small waist-worn sensor that recorded movement in multiple directions.
The study included 75 participants between the ages of 19 and 63. Activity levels ranged from largely inactive lifestyles to ultra-endurance running.
No Evidence the Body Cancels Out Exercise
The results showed that as people moved more, their total energy use increased accordingly. The body did not appear to compensate by dialing down energy use elsewhere. Essential functions such as breathing, blood circulation, and temperature regulation continued to require the same amount of energy, even as physical activity rose.
This means the body does not clearly offset or “cancel out” the extra calories burned through movement.
“Energy balance was a key piece of the study,” said Kristen Howard, senior research associate at Virginia Tech and the article’s lead author. “We looked at folks who were adequately fueled. It could be that apparent compensation under extreme conditions may reflect under-fueling.”
Less Sitting, More Moving
The researchers also observed a strong connection between higher activity levels and reduced time spent sitting. Simply put, people who move more tend to spend less time being inactive overall.
Taken together, the findings suggest that the long-debated idea that increased movement leads to increased calorie burn may be more accurate than some experts have assumed. While the results support the additive energy model, the researchers note that more work is needed. “We need more research to understand in who and under what conditions energy compensation might occur,” said Davy.
