Exercise doesn’t always help you lose weight

For many years, a simple formula has been used in the scientific world to determine total energy consumption. According to her, the sum of all calories burned per day is equal to the basic metabolism needed to maintain vital activity, plus the energy spent on physical exercise. This concept, known as the additive model, assumed that every calorie lost during exercise was simply added to daily consumption, promising an inevitable weight loss.

As an example, imagine that your body spends two thousand calories on a typical day, and then you go for a run, burning another four hundred. According to this logic, your total consumption will be two thousand four hundred calories. It was based on this simple mathematics that the belief was based that every additional activity leads to weight loss.

However, in recent years, another theory has been gaining popularity, offering a completely different view of metabolism. The new model suggests that our body has a certain limit on the total amount of energy it can expend. That is, if we increase calorie consumption through activity, our body is able to compensate for this by reducing the cost of other internal processes, such as cell repair or maintaining body temperature. Thus, those extra calories that you thought were successfully burned during your workout are actually only partially compensated.

Two researchers from Duke University in the USA, Herman Pontzer and Eric T. Trexler, took up the study of these two contradictory ideas. Their goal was to find out which of them is best supported by the available data.

For their comprehensive analysis, they studied fourteen different projects, which involved about four hundred and fifty people involved in special programs. Materials obtained during animal experiments were also taken into account. By comparing the estimated and actual energy consumption of the participants, the experts were able to determine how much the body compensated for the increased physical activity.

Their findings turned out to be very interesting. It turned out that the traditional additive model often overestimates how much the total daily energy consumption increases when exercising. On the contrary, it has been found that as activity increases, humans and animals can adjust their energy costs by reducing them to other processes or activities.

The data obtained show that, on average, about 72% of the calories spent on physical activity are actually added to the total daily expenditure. The remaining 28% can be neutralized by internal compensation. This means that exercise still contributes to an increase in total energy consumption, but to a lesser extent than the simple sum predicts. It is worth noting that the figure of 28% is an average and can vary greatly from person to person.

“Humans and other creatures respond to increased physical activity by reducing energy costs for other tasks, which confirms the model of limited energy consumption,” the researchers commented in their work.Such discoveries may explain why exercising in isolation often leads to less weight loss than expected, and why diet plays such a significant role in weight management.