When does metabolism start to drop? It’s much later than you might think, study shows

Your metabolism likely starts to tank much later than previously thought, a new study suggests.

A team of researchers — including Herman Pontzer, an associate professor of evolutionary anthropology at Duke University — found that the average person’s metabolism appears to peak at age one and starts to decline once they turn 60.

The study looked at the average calories burned by over 6,600 people in 29 countries, from one week old up to age 95, and found that metabolism largely remained steady throughout mid-life.

“There are lots of physiological changes that come with growing up and getting older,” Pontzer told Duke Today. “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.”

Researchers adjusted their measurements for body size and compared participants’ metabolism “pound-for-pound.”

The researchers’ findings, published in journal Science on Aug. 13, were grouped into four metabolic stages:

1. From birth to age one, a baby’s metabolism goes from being, on average, the same as the mother’s to “burn(ing) calories 50% faster for their body size than an adult.”
2. From then on, a person’s metabolism will slow down about 3% each year until their 20s when it “levels off into a new normal.”
3. No metabolism changes were recorded between 20 to 60 years old.
4. Metabolism will steadily decline after age 60 and by age 90 will be 26% lower than in mid-life.

The study’s findings now pose new unanswered questions for researchers.

“Something is happening inside a baby’s cells to make them more active, and we don’t know what those processes are yet,” Pontzer told Duke Today.

And even though teens undergo a number of growth spurts, researchers didn’t find a spike in “daily calorie needs” during puberty.

“We really thought puberty would be different and it’s not,” Pontzer told Duke Today.

Researchers were also surprised at the lack of metabolism changes in mid-life. If anything, metabolism during a person’s 20s, 30s, 40s and 50s was the most stable, according to the study.

Metabolism starts declining after age 60 and then it’s a 0.7% decline per year, the study suggests.

Lost muscle mass as people age may be partially to blame because “muscle burns more calories than fat,” according to researchers, who emphasized the declining muscle mass “is not the whole picture.”

“All of this points to the conclusion that tissue metabolism, the work that the cells are doing, is changing over the course of the lifespan in ways we haven’t fully appreciated before,” Pontzer told Duke Today. “You really need a big data set like this to get at those questions.”

This story was originally published August 17, 2021 at 3:03 PM with the headline "When does metabolism start to drop? It’s much later than you might think, study shows."

Karina Mazhukhina

McClatchy DC

Karina Mazhukhina is a McClatchy Real-Time News Reporter. She graduated from the University of Washington and was previously a digital journalist for KOMO News, an ABC-TV affiliate in Seattle.