Energy expenditure might have an upper limit
Another factor that may contribute to the lack of weight loss through exercise alone is that there may be a maximum limit to a body’s energy expenditure. In a study published by Herman Pontzer in 2016 in the journal Current Biology, Pontzer and his colleagues found that there was no correlation between an increase in physical activity and an increase in calorie burn. The researchers found that the correlation between physical activity and calorie burn is stronger when it involves lower levels of physical activity.
This demonstrates that there is a limit to how many calories the body can burn through physical activity. The body adapts to the increase in physical activity by reducing the amount of energy it burns. Pontzer calls this the constrained model where the body sets a limit on how much energy it will use when it becomes stressed over physical activity and limited food sources. Researchers are still investigating this hypothesis.
