Metabolism is a term that refers to the rate that we burn calories to keep our bodies functioning.
It is known that metabolism changes as the years pass, but very few details were known regarding the evolution of the changes.
A new study analyzing the evolution of the human metabolism over the generations made some interesting breakthroughs.
The researchers took data from over six thousand people from twenty-nine countries, with ages ranging from 8 days to 95 years old.
To track the effects of the metabolism, the researchers used isotopes placed in drinking water and analyzed them in urine, which led to an accurate estimate of the daily energy expenditure of all members of the study.
The data showed that pound-for-pound, the human metabolic rate peaks during infancy. In contrast to popular belief, during our teenage years, we are burning calories only slightly faster than when we are middle-aged.
To put it simply, you can’t blame your metabolism for the thickening lines around your waist and say that it used to be different when you were a teenager.
Herman Pontzer, an evolutionary anthropologist of Duke University, said:
“There are lots of physiological changes that come with growing up and getting older. Think puberty, menopause, other phases of life. What’s weird is that the timing of our ‘metabolic life stages’ doesn’t seem to match those typical milestones.”
Estimates suggest that the human metabolism slows down by roughly 3% until our 20s when it enters a steady state that persists until our 50s.
However, after reaching our 60s, it turns out that the metabolism slows down by approximately 0.7 per cent a year.
When a person reaches their 90s, they need 26% fewer calories than their middle-aged counterparts, partly due to a decrease in muscle mass but also due to their cells slowing down with age.
What’s more impressive is when you look at the energy consumption of infants – It turns out that, during the first year of life, we burn calories approximately 50% faster (for the body size) than a full-grown adult.
Pontzer explained that energy use is “rocketing” in the early stages of life.