What We Think We Know About Metabolism May Be Wrong

Nutrition
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https://www.nytimes.com/2021/08/12/health/metabolism-weight-aging.html

"Central to their findings was that metabolism differs for all people across four distinct stages of life.

There’s infancy, up until age 1, when calorie burning is at its peak, accelerating until it is 50 percent above the adult rate.

Then, from age 1 to about age 20, metabolism gradually slows by about 3 percent a year.

From age 20 to 60, it holds steady.

And, after age 60, it declines by about 0.7 percent a year.

Once the researchers controlled for body size and the amount of muscle people have, they also found no differences between men and women."

I wonder what this means for the theory that metabolism slows when you are dieting. My initial assumption is this refutes that theory.

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I’m not sure that it really addresses that. I think this is more of a broad stroke for overall averages vs individual rates based on diet, exercise, etc. I think it is pretty well proven that metabolic rates for individuals vary depending on certain conditions but this suggests that assuming all conditions equal, you can expect your metabolic rate to be similar from ages 20-60.

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Yeah, I think we know the answer to that question. Remember the study on the biggest loser contestants who found that their resting metabolic rate went down to 800 calories after the show? Part of that was weight loss rate though.

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I’ve always thought the people who said “Your body just changes when you hit 30…40… etc” were full of crap. Likely your lifestyle just changed significantly with marriage, job, kids, etc.

Certainly our ability to recover slows down, as I’m reminded every time I drink that third glass of wine at night……

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Agreed…we also know that metabolic rates will shift based on activity levels and other life factors (including diet).

RMR is not constant…I have access to a pretty large data set that pretty clearly demonstrates this.

Fun fact…the device that was used to measure RMR on TBL is from a subsidiary of ours. Very cool product…but unfortunately not a consumer device.

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My understanding is that when the body is in a chronic caloric deficit, it just won’t do certain things it used to do. For example, gymnasts losing their period. The body is saying that you are so skinny and don’t seem to be eating enough so I’m going to shut down reproduction to conserve energy.

Has anyone ever noticed that when they trained to overload that all they want to do is sit on the couch. You lose motivation and you don’t even want to walk up and down the stairs anymore. This is your body’s way of conserving energy.

Herman Pontzer, the author of the study that the article talks about wrote another book called Burn.

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I just finished Herman Pontzer’s book Burn.
It’s a fascinating read about how our metabolism works and has evolved since early on in evolution.
Busts a lot of myths about how our body uses the calories we consume. I recommend everyone read it.

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His work sheds a cruel light on calories in and calories out. You reduce calories and your body finds a way to reduce the calorie burn.

I haven’t heard the implications for athletes. Pontzer, I think has spoken/written about how it’s very hard to exercise off excess weight. I believe his theory is called the constrained energy model. For example, your regular daily calorie burn is 2000 calories per day. You do 500 calories of exercise. Your daily burn that day is not going to be 2500.

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This isn’t really a new revelation…it has been known for a long time. Metabolism / RMR is not a fixed number and can vary due to a number of factors, including changes in diet, exercise, age, etc.

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Nobody said it was.

Pontzer’s research showing that the daily calorie burn (different than RMR) stays in a tight range no matter how active you are is relatively new.

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Another podcast appearance by Dr. Pontzer: