Our Metabolism

Blaming those extra pounds on a slowing metabolism as you age? Not so fast.

A new international study counters the common belief that our metabolism inevitably declines during our adult lives. Well, not until we’re in our 60s, anyway.

Researchers found that metabolism peaks around age 1, when babies burn calories 50 percent faster than adults, and then gradually declines roughly 3 percent a year until around age 20. 

From there, metabolism plateaus until about age 60, when it starts to slowly decline again, by less than 1 percent annually, according to findings published Thursday in the journal Science.

To tease out the specific impact of age on metabolism, the researchers adjusted for factors such as body size (bigger bodies burn more calories overall than smaller ones) and fat-free muscle mass (muscles burn more calories than fat).

“Metabolic rate is really stable all through adult life, 20 to 60 years old,” said study author Herman Pontzer, an associate professor of evolutionary anthropology at Duke University and author of “Burn,” a new book about metabolism. 

“There's no effect of menopause that we can see, for example. And you know, people will say, 'Well when I hit 30 years old, my metabolism fell apart.' We don't see any evidence for that, actually.”

Pontzer and colleagues studied a database of more than 6,400 people, ages 8 days to 95 years, from 29 countries worldwide who had participated in “doubly labeled water” tests. 

With this method, individuals drink water in which some of the hydrogen and oxygen have been replaced with isotopes of these elements that can be traced in urine samples.  READ MORE