Physical activity does more than just keep you fit during the workout—it continues to affect your body even after you stop moving.
A new study from Virginia Tech, working with researchers from the University of Aberdeen and Shenzhen University, found that being active increases the total amount of energy your body uses in a day.
Importantly, the body does not reduce energy use in other areas to make up for the calories burned by exercise.
This matters because while the health benefits of exercise are well known, there’s been less clarity about how physical activity affects what scientists call the “energy budget”—how your body divides its daily energy across different functions like breathing, thinking, digestion, and movement.
Some experts believed that the body works like a fixed salary: if you burn more energy through exercise, your body might save energy elsewhere, such as by slowing digestion or other functions.
Others thought the body works more like a commission-based job, where you can keep adding to your energy use without cutbacks in other areas. The research team wanted to find out which model is true.
To do this, they studied how much energy people burn each day and how active they are. The study included 75 participants between the ages of 19 and 63, with physical activity levels ranging from people who were mostly inactive to ultra-endurance runners.
To track energy use, the researchers used a special method involving isotopes—versions of oxygen and hydrogen that act like tracers in the body.
Participants drank water with these isotopes, and researchers collected their urine over two weeks. By measuring how much of each isotope was lost, the team could calculate how much carbon dioxide the body produced, which is a direct way to estimate calories burned.
Participants also wore small sensors on their waist that measured how much they moved and in what directions.
The findings were clear: the more physically active someone was, the more total energy they burned each day. Even better, the body did not try to “save” energy by cutting back in other areas. In other words, all the extra calories burned through movement were added to the total daily energy use.
For example, functions like breathing, pumping blood, and keeping your body temperature steady continued at the same rate regardless of how active a person was. So, increasing movement really does increase how many calories you burn in a day.
Lead author Kristen Howard explained that the people in the study were getting enough food to meet their needs, which might explain why the body didn’t cut back elsewhere. Under very extreme conditions or when someone is not eating enough, the body might react differently.
Another interesting finding was that people who moved more also spent less time sitting. So staying active not only burns more calories—it also helps reduce the amount of time you’re inactive, which is known to be bad for health.
This study supports the idea that being more active truly helps increase how much energy your body uses. While there’s still more to learn about when and why the body might adjust its energy use, this research confirms that regular movement can boost your daily calorie burn without slowing other body processes.
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The study is published in PNAS.
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