Experts bust popular myth about body reversing workout effects - Video

Think your body cancels out the calories you burn by moving more? Think again. A new study published in Proceedings of the National Academy of Sciences reveals that physical activity truly adds to your daily energy output, without the body compensating by saving energy elsewhere. Led by scientists from Virginia Tech, the University of Aberdeen, and Shenzhen University, the research shows that every bit of movement—from walking the dog to marathon training—directly contributes to more calories burned overall.

Exercise has long been praised as vital for heart, brain, and metabolic health, but until now, scientists debated whether our total “energy budget” could actually expand with physical activity. One idea proposed that when we move more, our body pulls energy away from other systems, like digestion or temperature regulation, to keep calorie use stable. The rival theory—the additive model—suggests that moving more truly increases daily energy expenditure without taking away from other functions.

To test which model holds up, the research team studied 75 adults aged 19 to 63 with activity levels ranging from sedentary lifestyles to ultra-endurance training. Each participant’s daily energy use was measured using the gold-standard “doubly labeled water” technique, where participants drink water containing special forms of hydrogen and oxygen. By analyzing how quickly these isotopes left the body through breath and urine, scientists precisely calculated total daily calories burned over two weeks. Physical activity was tracked continuously using small waist-worn sensors.

The results were clear: people who moved more burned more energy, full stop. The body didn’t offset this by cutting back on other essential processes like heart function, breathing, or temperature regulation.

Interestingly, those who were more active also spent less time sitting, further boosting their calorie use. The findings support the additive energy model—meaning every bit of movement, no matter how small, truly counts. For maintaining energy balance and long-term health, more movement really does mean more calories burned.

REFERENCE: Kristen R. Howard, Olalla Prado-Nóvoa, Guillermo Zorrilla-Revilla, Eleni Laskaridou, Glen R. Reid, Elaina L. Marinik, Marina Stamatiou, Catherine Hambly, Brenda M. Davy, John R. Speakman, Kevin P. Davy. Physical activity is directly associated with total energy expenditure without evidence of constraint or compensation. Proceedings of the National Academy of Sciences, 2025; 122 (43) DOI: 10.1073/pnas.2519626122