New research into how exercise impacts the body’s ‘energy budget’ has shown that physical activity adds to the total energy used without triggering energy conservation.
While the benefits of staying active are well known, less is understood about how exercise impacts on the allocation of energy to different bodily processes.
Experts have previously suggested that the body’s ‘energy budget’ works either by energy being taken from other bodily functions to cover the expenditure of movement, or by being more flexible and additive so that increased energy use is allowed for.
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A team of researchers from Virginia Tech, the University of Aberdeen and Shenzhen University set out to explore which of the two model applies and how the energy budget is impacted by physical activity.
They did this by analysing total calories burned in a day by people undertaking a varying degree of physical activity.
The team found that the body continued to work at its usual rate when someone was active, rather than conserving energy in one area to compensate for calories burned.
In practical terms, this meant that functions such as breathing, maintaining temperature and blood circulation remained stable.
The study’s principal investigator, Professor Kevin Davy, said: “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.”
The participant group was made up of 75 adults aged from 19 to 63, with activity levels ranging from sedentary to taking part in endurance running.
Activity was measured by participants wearing a sensor around the waist, while energy expenditure was measured by giving participants drinks containing isotopes of oxygen and hydrogen, then calculating the difference in the amount of isotopes lost in proportion to the amount of carbon dioxide produced.
The study’s lead author, senior research associate at Virginia Tech, Kristen Howard, said: “Energy balance was a key piece of the study. We looked at folks who were adequately fuelled. It could be that apparent compensation under extreme conditions may reflect under-fuelling.”
Professor Davy added: “We need more research to understand in whom and under what conditions energy compensation might occur.”
The findings also showed that people who were more active were less likely to spend longer periods of time not moving.
