According to research, it at least doesn’t track the way that people conjectured: https://www.nytimes.com/2021/08/12/health/metabolism-weight-aging.html.
In fact, look closely at that screenshot from the 1978 Lancet paper, and you find this has been a known fact for over 40 years.
The highest measured metabolism I’ve ever seen was in a post-menopausal woman with over 200lbs to lose (her stated goal). She was the client of an employee of mine. Her MEASURED (I want to be clear I’m not talking estimated or mathematically approximated; we hooked her up to an oxygen exchange mask to MEASURE) metabolic rate at rest clocked in over 7,000 calories per day. This is AT REST. When I was 22 years old, my measured resting rate was about 2,400. At age 37, my measured resting rate was over 3,000 while six days fasted.
Here’s the real kicker: when children are GROWING MORE BODY MASS their average metabolic rates are 5600 in non-obese adolescent males and 7223 in obese adolescent males: https://pubmed.ncbi.nlm.nih.gov/7562278/ . GAINING weight is the highest metabolic rate.
Larger people have higher metabolisms. Smaller people have lower ones. People growing more body mass have higher metabolisms. People losing body mass have lower ones.
Everything you’ve ever said or heard or read or thought about metabolism is mostly wrong. Even if it was accidentally right, it was for the wrong reasons. An older person may measure a slower metabolism simply because skeletal and muscle mass is less, they eat less, and they’re both weaker and less active. Age didn’t do it. Choices did. Gender didn’t do it. Strength or loss of strength did.
Moreover, as always, we are confronted with the meaninglessness of metabolic RATE. The rate doesn’t matter AT ALL. Higher rates are correlated to growth, if anything. We don’t want faster. We want BETTER distribution of metabolic effort. If rate improves, so be it. But what we care about is NET distribution of effort.
I don’t know why, but people cannot seem to grasp this concept. If you spend 2 million dollars and one penny per year but only make 2 million per year, you don’t gain wealth. You’re on the street in a matter of months. The average person thinks making 1 million is amazing. Making 1 million is nothing if expenses are high. The equation for finances is bigger than a simple-minded earnings or top line revenue number. Likewise, a 7,000 calorie per day metabolism sucks if that’s all aimed at growing fat tissue. While starving, all that’s happening is that person is burning up 4lbs of muscle and tendons every day. They’re getting fatter.
Conversely, a person who makes 70k per year, but wisely invests 30 each year will be a multi-millionaire in 25 years. Likewise, a person with an 800 calorie per day resting metabolism will be fittER when investing effort appropriately. Time works on your side when you work the system intelligently. "Getting older" is only worse if you made decisions to worsen your landscape.
Strengthen. Focus on micronutrient and protein sufficiency. 800 is no problem. If you eat like an idiot and refuse to be active, it doesn’t matter if you have a 7,000 calorie per day metabolism. If you spend like an idiot and refuse to invest, it doesn’t matter if you make millions of dollars per year.
The NET outcome is a result of the total influences. One single line of input/income or rate doesn’t tell us much about the final output. Where the effort goes tells us a lot more.