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Representative image. | Photo credit: iStock images
Highlights
- In the study, the researchers gathered huge amounts of data from 6,421 people from 29 countries, all in a wide age range ranging from 8 days to 95 years old.
- Contrary to what we originally thought, the study found that, pound for pound, our metabolic rate is actually highest when we’re infants.
- After the age of 20, our metabolism reaches a plateau until the age of 60, then begins to gradually decline at a rate of less than 1% per year.
The next time you want to blame those extra pounds for your age, you might want to think again. For some time now, we’ve known that metabolism – the rate at which our body burns calories to generate the energy it needs – changes with age, but there isn’t much else we could say about how it actually unfolds in our lifecycle.
Today, a new international study assessing metabolism across generations has shattered some common misconceptions about metabolism, paving the way for a new relationship between metabolism and age to be explored. In the study, the researchers gathered huge amounts of data from 6,421 people from 29 countries, all in a wide age range ranging from 8 days to 95 years old.
Participants performed “double-labeled water tests” – a method by which individuals are required to drink water in which some of the oxygen and hydrogen have been replaced by isotopes of the same elements. so that they are traceable in urine samples. In doing so, the researchers were able to determine a daily energy expenditure for each participant. The study was also adjusted for various factors such as body size – larger bodies burn more calories than smaller ones – and fat-free muscle.
And contrary to what we originally thought, the study found that, pound for pound, our metabolic rate is actually highest when we’re infants. Metabolism peaks around age 1, when babies burn calories about 50% faster than adults, and then begins to decline by about 3% each year until age 20. After 20 years, our metabolism plateaued every until the age of 60, where it then begins to gradually decline at a rate of less than 1 percent per year.
“There are a lot of physiological changes that accompany growth and aging,” says Herman Pontzer, associate professor of evolutionary anthropology at Duke University and author of “Burn,” a new book on metabolism. “Think about puberty, menopause, other phases of life. What is strange is that the timing of our “metabolic life stage” does not seem to correspond to these typical stages. “
The researchers also found that by the time a person turns 90, they need an average of 26% fewer calories each day than a middle-aged person. This is particularly interesting because it confirms that it is not only a loss of muscle mass that is responsible for slowing down the metabolism, but a fundamental change in our cells.
The other striking finding is how much energy the body actually needs in the first 12 months of life. “Something is going on inside a baby’s cells to make them more active, and we don’t yet know what those processes are,” says Pontzer.
With the latest study being so comprehensive and using such a large dataset, it will go a long way in isolating how metabolism varies from other ways our bodies change and evolve with age. Research may also be helpful in structuring treatment plans for people of different ages.
“All of this leads to the conclusion that tissue metabolism, the work that cells do, evolves over the course of life in ways that we have not fully appreciated before,” explains Pontzer.
“You really need a big data set like this to answer these questions. “
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