There is a limit to everything

We all must have heard motivational phrases like “there is no limit to what humans can do” and “it’s all in your head”. But according to researchers at Duke University in the United States, there is a limit to what the human body can endure and it is in your gut.

A new study says humans can only burn calories at 2.5 times their resting metabolic rate. When it comes to physical activities lasting days, weeks and months, not even the world's fastest marathoner can surpass this limit.

During the study, the team of researchers measured daily calories burned by a group of athletes who ran six marathons a week, for five months. After 20 weeks of high endurance tests, the team found the athletes were burning 600 calories fewer per day than expected which ultimately made them reach their conclusion.

Researchers also considered other feats of human endurance like pregnancy. Also, energy expenditure found in endurance athletes was almost similar to the metabolic rates of women during pregnancy

The study shows that beyond 2.5 times, the body starts to break down its own tissues to make up for the caloric deficit. One explanation for this limit may be the digestive tract's ability to break down food. This new finding challenges the previous idea that human endurance is linked to the body’s ability to regulate its temperature.