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Research Shows That Exercise Does Not Drain Your "Energy Budget" — It Adds To It

Author: Alexandra Engler

April 08, 2026

Senior Beauty & Lifestyle Director

By Alexandra Engler

Senior Beauty & Lifestyle Director

Alexandra Engler is the senior beauty and lifestyle director at mindbodygreen and host of the beauty podcast Clean Beauty School. Previously, she's held beauty roles at Harper's Bazaar, Marie Claire, SELF, and Cosmopolitan; her byline has appeared in Esquire, Sports Illustrated, and Allure.com

Image by Prostock-Studio

April 08, 2026

For years, researchers have debated how your body uses energy. Do you have a set limit on how many calories you can burn a day, or can your energy expenditure continue to rise with movement? A groundbreaking new study just put this to the test.

Here's what the science actually shows, why this matters for your fitness routine, and what it means for building sustainable, energizing movement habits that support long-term health.

The myth: Your body has a fixed "energy budget"

There are two main trains of thought when it comes to energy expenditure.

One, called "constrained energy expenditure"1, states that your body has a set amount of energy it's willing to burn each day. If you ramp up your exercise, your metabolism compensates by dialing down energy expenditure elsewhere—maybe by suppressing immune function, reducing reproductive hormones, or slowing thyroid activity.

The implication? That there's a ceiling to how much you can increase your total daily energy expenditure through exercise. It sounds plausible.

But according to this new study, we can officially deem this a myth.

What the new research found: A direct, linear relationship

The study, published in the Proceedings of the National Academy of Sciences from researchers at Virginia Tech, specifically set out to understand how physical activity impacted overall energy expenditure.. Essentially, does working out drain the body’s "energy budget"? Or does the budget increase with movement?

- Following 75 participants between the ages of 19 and 63 for two weeks, the researchers measured folks who engaged in a wide range of activity levels, from sedentary to ultra-endurance running.

- Participants drank special forms of oxygen and hydrogen and gave urine samples over two weeks. Because oxygen leaves the body as both water and carbon dioxide—while hydrogen exits only as water—researchers could track the difference to estimate how much energy participants used.

- Physical activity was measured with a small waist-worn sensor that tracked movement throughout the day.

- With this method, the researchers were able to measure total energy expenditure, meaning the total number of calories burned in a day.

What they found was clear: Physical activity and total energy expenditure have a direct, linear relationship. The more active you are, the more total energy your body uses. Full stop.

What made the findings so strong is that no metabolic compensation was detected. Researchers found zero evidence that your body reduces energy expenditure elsewhere when you exercise more.

In addition, they found no biomarker suppression. Physical activity wasn't associated with changes in immune markers, reproductive hormones, or thyroid function—the very systems the "constrained energy" theory claimed would get dialed down.

An important caveat about calorie input

This study looked at individuals who were "adequately fueled,” meaning none of the participants were in a calorie deficit. The researchers note that metabolic compensation may still occur in situations that a person is under-fueling; however more research is needed to understand if that’s the case.

How your body actually uses energy

To understand why this matters, it helps to know where your daily energy expenditure actually goes. Your total daily energy expenditure (TDEE) breaks down into a few key components:

- Basal metabolic rate (BMR): The energy your body uses just to keep you alive—breathing, circulating blood, maintaining body temperature, supporting organ function. This accounts for about 60-70% of your total daily calories burned.

- Thermic effect of food (TEF): The energy required to digest, absorb, and process the food you eat. This is roughly 10% of TDEE.

- Physical activity: Both structured exercise and non-exercise activity thermogenesis (NEAT)—all the movement you do throughout the day, from walking to the car to fidgeting at your desk. This is the most variable component and can range from 15-30% or more of TDEE, depending on how active you are.

The "constrained energy" theory1 suggested that if you increased physical activity, your body would compensate by reducing BMR or NEAT. But this new research shows that doesn't happen in any meaningful, systematic way.

Your metabolism isn't a fixed pie where one slice grows and another shrinks. It's more dynamic and responsive than that—and it genuinely responds to the de