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Engaging in physical activity provides countless advantages, such as reducing the impact of chronic illnesses like anxiety, depression, cardiovascular disease, and hypertension. In many ways, it is a crucial element for maintaining overall well-being.
Yet, recent scientific findings reveal that being active does not result in a substantial, long-term rise in daily calorie expenditure.
“Your daily habits don’t dramatically influence the number of calories you expend, at least not in a straightforward manner,” explained Herman Pontzer, an evolutionary anthropologist at Duke University and author of Burn: New Research Blows The Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy.
Our bodies are designed to consume a fairly consistent amount of energy daily, which remains largely unchanged whether a person is sedentary or physically active, provided they are of the same weight.
Daily calorie expenditure remains relatively stable
When beginning a new fitness routine, you may initially burn additional calories, but within a few months, your body adjusts, keeping your total energy use within a limited range.
“The body adapts to long-term shifts in calorie expenditure,” noted Samuel Urlacher, an evolutionary anthropologist at Baylor University who works with Pontzer. “Regular exercisers don’t burn as many calories as standard formulas suggest.”
This idea, known as constrained daily energy expenditure, is a newer concept in fitness and nutrition. It has been validated by comparing the energy needs of traditional hunter-gatherers, who engage in significant physical activity, with those of sedentary individuals.
Sedentary and active individuals burn roughly the same number of calories on average
Pontzer, Urlacher, and other researchers have found that both highly active hunter-gatherers and sedentary individuals burn, on average, the same daily calories when adjusted for weight. The distinction lies in how they expend energy, not the total amount.
Initially, it was thought that active individuals might offset their energy use by being less active at other times or moving more efficiently. However, the reality seems to be more nuanced.
The body allocates a significant portion of energy to vital functions that aren’t as noticeable as physical activity. “Even with regular exercise, more than 50% of your calories are spent on basic bodily functions at rest,” Pontzer explained.
This energy is used for critical systems like the immune system, stress response, reproductive functions, and the brain. “Your brain alone consumes about 300 kilocalories daily,” Pontzer noted. “That’s like running a 5K every day.”
Unused energy from lack of exercise is redirected to other bodily functions
The theory suggests that when the body has surplus energy—a rarity throughout most of human history—it allocates it to beneficial but lower-priority processes. “In today’s high-energy environment, your body can continuously focus on these lower-priority tasks,” Pontzer explained.
A useful comparison is to imagine this like managing a household budget. If you’ve always lived paycheck to paycheck and suddenly receive extra money, you’d likely spend it on something impactful but outside your usual expenses. You wouldn’t adjust your overall budget because the extra income isn’t guaranteed.
Our bodies, evolved to function on a tight and often unpredictable energy budget, treat the additional energy from sedentary living as a temporary surplus. This energy must either be utilized or lost.
Inactive lifestyles result in heightened inflammatory and stress reactions
If your body isn’t using calories for physical activity, it will allocate them to less critical but energy-intensive functions, such as inflammation and stress responses.
In moderation, inflammation and stress responses defend against pathogens and help us react to threats. However, when these responses become chronic, they can harm blood vessels and tissues, leading to various health problems.
Individuals with highly sedentary lifestyles often exhibit higher chronic inflammation and an exaggerated stress response, including elevated cortisol and adrenaline levels. In contrast, active individuals tend to have lower inflammation and a more balanced stress response. However, active people who don’t consume enough calories may experience slower recovery from injuries or infections due to insufficient energy for the immune system.
Our bodies’ energy usage is still shaped by an evolutionary past where energy was scarce, and inflammatory or stress responses were vital for survival.
The issue today is that we live in an energy-abundant environment, which can harm our bodies. “This is what we call an evolutionary mismatch,” Urlacher stated. “Our biology hasn’t adapted quickly enough to these rapid environmental changes.”
Select physical activities based on enjoyment, not calorie burn
This perspective is liberating: Exercise enhances health and happiness in meaningful, measurable ways that extend far beyond calorie expenditure. It boosts mood, helps prevent or manage chronic conditions, and brings joy by enabling the strength and energy to live life fully.
With calorie burning no longer the primary focus, you can prioritize finding activities you genuinely love—movement that brings you joy, makes you happy, and motivates you to stay consistent, regardless of calorie counts.
Instead of tracking exercise calories, concentrate on discovering activities that suit your preferences, allowing you to reap the numerous benefits of regular physical activity.
As for your diet, aim for a consistent intake focused on nutritious, healthy foods.
“No amount of exercise can compensate for poor eating habits,” Urlacher remarked.
