Daily energy expenditure through the human life course, 2021, Pontzer et al

Abstract

Total daily energy expenditure (“total expenditure”) reflects daily energy needs and is a critical variable in human health and physiology, but its trajectory over the life course is poorly studied. We analyzed a large, diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 years. 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.

Paywall, https://science.sciencemag.org/content/373/6556/808


Journal summary of study.

Summary

Metabolism is not just about energy—how the body handles nutrient fuel and converts it to useable energetic currency. Metabolism also encompasses synthesis, modification, and exchange of the building blocks for all aspects of cellular function and acts as a sensor and regulator of cellular activities, in which individual moieties within metabolic pathways influence cellular responses. A substantial amount of the energy taken in each day is required to simply sustain life; the energetic demands of physical activity are superimposed on a vastly integrated machinery. Metabolic status has been linked to innumerable diseases and disorders, including those most prevalent with age (1–3). On page 808 of this issue, Pontzer et al. (4) analyze energy expenditure in more than 6400 males and females from 29 countries across the globe, aged between 8 days and 95 years, and show distinct metabolic phases during development and aging.

Paywall, https://science.sciencemag.org/content/373/6556/738

 

The actual paper is here (again, paywalled): https://science.sciencemag.org/content/373/6556/808

 

Metabolism peaks at age one and tanks after 60, study finds

"Middle-aged spread cannot be blamed on a waning metabolism, according to an unprecedented analysis of the body's energy use.

The study, of 6,400 people, from eight days old up to age 95, in 29 countries, suggests the metabolism remains "rock solid" throughout mid-life.

It peaks at the age of one, is stable from 20 to 60 and then inexorably declines.

Researchers said the findings gave surprising new insights about the body."

https://www.bbc.co.uk/news/health-58186710

 

Yeah, sorry, I spotted that and was editing my original post to add it in when you posted this.

 

Many people believe metabolism ramps up in teenage years, peaks in 20s, and declines from 30s, as has been taught in the past. This study disproves this.

 

In order for a person to be able to "do things" their body needs to be able to supply energy at a rate over and above what is demanded by its own life-support systems. Vaguely akin to the way an idling engine in a car is consuming energy even when the car is stationary. More power is required in order to do anything more than that.

 

Google "does metabolism slow down with age"

Then look at the results, as well as the sample answers from the "People Also Ask" section. Every answer from every webpage would be wrong according to this study, e.g., https://www.saltlakeregional.org/newsroom/2017-01-20/how-your-metabolism-changes-you-age and https://www.piedmont.org/living-better/why-metabolism-slows-as-you-age

 

I was puzzled about this with regards to women going through the menopause who often put on weight. I was one of them and I put an enormous amount of weight on within 6 months to the extent that people who knew me thought I was pregnant. This was 20 years ago but I recall it well as it was quite embarrassing - I worked on a mobile library and at least 3 of my regulars put their foot in it. I was eating the same foods and doing the same things.....

In retrospect I believe in my case that it was the beginning of my thyroid problems. I had been underactive and on thyroxine for a few years but I think it stopped working for me but I didn't realise it for some years. ie my body could not convert the T4 to T3 in my body. I am on T3 only now, but it's controversial and the need is not recognised by many endocrinologists.

So this study is saying that metabolism remains stable, but I am betting that for many women it just doesn't because of the thyroid factor which is very common in women in middle age in particular.