After a long run or sweaty yoga session, all we want to do is flop down on the couch and catch our breath. But while we may temporarily feel tired after a workout, a new study supports the idea that exercise actually adds to our body’s daily “energy budget” — it doesn’t deplete it.
There are two leading theories about how workouts impact our bodies’ energy expenditure. One posits that we have a set amount of energy we can “spend” in a day. If we use a portion of it on exercise, our bodies conserve some in other ways, like by suppressing our immune system (which can be a good or bad thing, depending on the level of exercise).
But researchers have now found more evidence in favor of the other theory, which states that our energy budgets are flexible and additive, meaning physical activity allows for an increase in the total amount of energy a person spends.
“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,” principal investigator Kevin Davy said in a news release.
Over a two-week span, the researchers tracked the physical activity of 75 participants, ages 19 to 63, with a wide range of activity levels. During the same timeframe, participants also drank specific forms of oxygen, which is expelled from the body as water and carbon dioxide, and hydrogen, which leaves as only water. The team then collected urine samples and measured the difference between the eliminated isotopes, which helped them assess the amount of carbon dioxide produced and gave them an idea as to how much energy the subjects had used.
They learned that not only was there no association between physical activity and resting metabolic rate — meaning participants didn’t later conserve energy based on how much they worked out — but they also experienced no immune, reproductive, or thyroid suppression in relation to their exercise levels. The findings led lead author Kristen Howard to speculate that being in a calorie deficit, rather than upping physical activity, may cause the energy conservation observed in research supporting the fixed budget theory.
“Energy balance was a key piece of the study,” she said. “We looked at folks who were adequately fueled. It could be that apparent compensation under extreme conditions may reflect under-fueling.” However, Davy added that “we need more research to understand in who and under what conditions energy compensation might occur.”
But the team also uncovered another reason to keep up with your workout routine: Those who were more physically active were less likely to stay sedentary for long stretches of time, which has been linked to negative health outcomes even for those who work out regularly.
Motivated to get moving? Check out our guides on the benefits of walking and weight lifting to learn how you can get started.
RELATED: The Benefits of Morning Exercise — And 5 Workouts You Can Try Today
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