From The Desk Of Clarence Bass
The Bottom-Line on Metabolism
In 1997, I wrote an article titled “The Metabolism Myth” explaining that there is no biological reason to get fat as we grow older.
Men and women in the Western world do, on average, suffer from creeping obesity. The average 35-year-old male gains about a pound of fat each year until the sixth decade of life. Women often gain proportionately more. The reason, however, is not an aging metabolism, but rather slowing down while eating the same or more.
Inactivity results in loss of muscle. And loss of muscle, not an aging metabolism, is the primary cause of creeping obesity. The muscle that remains is as metabolically active as ever.
It comes down to this: Your metabolism won't slow down if you don't.
You’ll find the entire article on this website:
An impressive new study - getting lots of attention - reported in the journal Science, finds essentially the same thing.
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Principle researcher Herman Pontzer, an evolutionary anthropologist at Duke University (and author of the best seller BURN, a new book about metabolism), and his colleagues found that there are four phases of metabolic rates from 8 days to 95 years, and that the slowdown in adults doesn’t occur until after 60. The longest phase runs from 20 to 60. Controlling for factors such as body size and muscle mass, there was no slowdown from 20 to 60.
The controls are key, because bigger bodies burn more calories and muscle is the fat burner, not fat. Simply put, fat is metabolized but it does not metabolize.
While we were not able access the entire study, the four phases of metabolism are detailed in the Abstract:
Total expenditure increased with fat-free mass in a power-law manner, with four distinct life stages. Fat-free mass–adjusted expenditure accelerates rapidly in neonates to ~50% above adult values at ~1 year; declines slowly to adult levels by ~20 years; remains stable in adulthood (20 to 60 years), even during pregnancy; then declines in older adults. These changes shed light on human development and aging and should help shape nutrition and health strategies across the life span.
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Gina Kolata reported the comments of several experts in the New York Times. Two were very excited, another not so much.
“It will be in textbooks,” predicted Leanne Redman, an energy balance physiologist at Pennington Biomedical Research Institute in Baton Rouge, La., who also called it “a pivotal paper.”
Rozalyn Anderson, a professor of medicine at the University of Wisconsin-Madison, who studies aging, wrote a perspective accompanying the paper. In an interview, she said she was “blown away” by its findings. “We will have to revise some of our ideas,” she added.
But the findings’ implications for public health, diet and nutrition are limited for the moment because the study gives “a 30,000-foot view of energy metabolism,” said Dr. Samuel Klein, who was not involved in the study and is director of the Center for Human Nutrition at the Washington University School of Medicine in St. Louis. He added, “I don’t think you can make any new clinical statements” for an individual. When it comes to weight gain, he says, the issue is the same as it has always been: People are eating more calories than they are burning.
I’m inclined to agree with Dr. Klein.
As I was reminded by one of the friends who alerted me to the new study: “I think you’ve been saying this!”
Ditching the metabolism excuse clears the way for more self-help: get moving in the gym and outdoors, and focus on eating sensibly.
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Jacqueline Stenson reported the study for NBC News, adding more comments and details from experts, including Dr. Pontzer.
Pontzer cut to the chase early on: “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.
“By calculating how much hydrogen you lose per day, and how much oxygen you lose per day, we can calculate how much carbon dioxide your body produces every day,” Pontzer explained. “And that's a very precise measurement of how many calories you burn every day, because you can’t burn calories without making carbon dioxide.”
The researchers analyzed average total daily energy expenditures, which include the calories we burn doing everything from breathing and digesting food to thinking and moving our bodies.
“…We didn't have a good sense of how that changes over the course of a lifespan,” Pontzer said. “You need really big data sets to be able to answer that question. And this was the first time that we had the ability to do this with a really big data set that would allow us to pull apart the effects of body size and age and gender and all these things on our energy expenditures over the day.”
Steven Malin, an associate professor of kinesiology and health and director of the Rutgers Applied Metabolism and Physiology Laboratory, called the study results “illuminating on something that we thought we know a lot about and realize that there's more to be discovered.”
Malin said the findings, for instance, contradict the belief that adults experience a decline in metabolism as they move from their 20s into their 30s and that this may be contributing to the obesity epidemic.
“It's not as if the weight gain is occurring because you don't ‘burn the same calories’ anymore,” he said.
You’ll find more about the significance of this break-through study on NBC News:
Metabolic decline is said to begin in earnest at 60.
PS: For a more complete view of my training results, see our Training Pictorial from 15 to 83: https://www.cbass.com/PICTORAL.HTM
October 1, 2021
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