You might think that the more you exercise, the more calories you burn. After all, that’s the basic principle of weight loss, right? Well, not exactly. According to a surprising study, the human body has a limited daily energy budget that does not increase with higher levels of physical activity. In other words, whether you are a couch potato or a marathon runner, you burn the same amount of calories per day.
How is that possible? The study, published in Scientific American, compared the energy expenditure of modern humans and traditional hunter-gatherers, who have very different lifestyles. The hunter-gatherers walk long distances, climb trees, and hunt for food, while the modern humans sit in offices, drive cars, and shop in supermarkets. The researchers expected to find that the hunter-gatherers burned more calories than the modern humans, but they were wrong. “The most surprising finding was that the more physically active a person was, the fewer calories he or she burned per day,” the article says.
The explanation is that the human body adapts to different levels of activity by adjusting its metabolism and energy allocation among various physiological functions. “The body has a way of compensating for the extra work by reducing energy spent on other physiological activities,” the article explains. For example, the body may lower its resting metabolic rate, reduce its immune system activity, or decrease its reproductive function. These adjustments help the body maintain a stable energy balance and avoid starvation.
This discovery has important implications for understanding human evolution and health. The study suggests that physical activity was not a major factor in the development of obesity, which is more likely caused by changes in diet and environment. The study also shows that physical activity has many health benefits beyond calorie burning, such as improving cardiovascular health, reducing inflammation, enhancing mood, and preventing chronic diseases. However, the effects of physical activity on energy balance are complex and multifaceted, and vary widely among individuals due to genetic, environmental, and behavioral factors.
The measurement of human energy expenditure is a key component of understanding human physiology, health, and disease. The amount of energy we expend during exercise is influenced by our body size, age, sex, fitness level and the intensity, duration and type of exercise we do. Physical activity can also influence energy intake by affecting appetite and food preferences. Therefore, to achieve a healthy weight and lifestyle, it is important to consider both the quantity and quality of physical activity and energy intake.
– The Exercise Paradox, Scientific American, February 1, 2017
– Physical activity and energy expenditure in humans, SpringerLink, October 12, 2021
– How to measure your energy expenditure during exercise, The Conversation, October 11, 2021
– Physical activity and energy balance: implications for obesity prevention and management, Nature Reviews Endocrinology, October 8, 2021