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Most of us remember that there was a time when we could eat whatever we wanted without getting fat
.
But a new study shows that our metabolism, that is, the rate at which we burn calories, will inevitably begin to decline after reaching its peak early in life, and this time may be later than imagined
The results of this study were published in the August 12th issue of Science
.
Herman Pontzer, associate professor of evolutionary anthropology at Duke University and author of the study, said: "As we grow and get older, there are many physiological changes
.
Think about puberty, menopause, and other stages of life
Pontzer and an international team of scientists analyzed the average calories consumed in daily life by more than 6,600 people from just one week to 95 years old in 29 countries around the world
.
In the past, most large-scale studies measured the energy consumed by the body to perform basic vital functions such as breathing, digestion, and pumping blood.
In other words, the calories needed to sustain life
.
But this only accounts for 50% to 70% of the calories we burn every day
In order to get the figure of total daily energy consumption, the researchers adopted the "doubly labeled water method" (doubly labeled water, bio-pass) method
.
This is a urine test that requires a person to drink water.
Since the 1980s, scientists have been using this technology to measure human energy consumption, but due to cost issues, the scale and scope of research have been limited
.
This technique is considered the gold standard for measuring daily energy consumption in daily life outside the laboratory
The research team collected and analyzed energy consumption throughout the life cycle and found some surprising results
.
"Some people think that their teens and twenties are the age at which their calorie-burning potential reaches its peak, but studies have shown that infants have the highest metabolic rate relative to their weight
.
"
In the first 12 months of life, energy requirements will increase rapidly.
Therefore, by the time they are one year old, one-year-old children burn 50% faster than adults in terms of their body size
.
This is not just because the baby has tripled from birth weight at one year of age
.
Pontzer said: "They are growing and their energy consumption is soaring, exceeding your expectations of their size and composition
The vigorous metabolism of infants may explain to a certain extent why children who do not get enough food during this developmental window are unlikely to survive and grow into healthy adults
.
Pontzer said: "Something is happening in the cells of babies to make them more active, but we don't yet know what these processes are
.
"
After the initial surge in infancy, data shows that metabolism slows by about 3% every year until we reach our 20s, and then it stabilizes and enters a new normal state
.
Surprisingly, after the researchers considered body size, the growth spurt during adolescence did not produce an increase in daily calorie requirements
.
Another surprise is that people’s metabolism is most stable between their 20s and 50s
"We really thought that adolescence would be different, but it is not the case
.
"
Middle-aged life is another surprise
.
Someone may have told you that after the age of 30, your weight will drop
.
Although there are several factors that can explain the thickening of the waist that often occurs during the golden age of our work, the results of the study show that changes in metabolism are not one of them
.
In fact, researchers have found that energy expenditure is the most stable during the period of 20s, 30s, 40s and 50s
.
Even during pregnancy, as the baby grows, as the weight increases, women's calorie needs will not be much more than expected
.
The data shows that our metabolism does not really start to decline until after 60 years of age
.
The slowdown is gradual, only 0.
7% per year
.
But a person in his 90s needs 26% less calories a day than a middle-aged person
.
Researchers say that with age, the loss of muscle mass may be part of the reason, because muscle burns more calories than fat
.
But this is not all
.
"We controlled the muscle mass," Pontzer said.
"This is because their cells are slowing down
.
"
Even taking into account different levels of activity, these models are still valid
.
Pontzer said that for a long time, it has been difficult to analyze what drives changes in energy consumption, because aging is closely related to many other changes
.
But this research supports the view that this is not just an age-related change in life>
.
"All these studies point to the conclusion that tissue metabolism, the work done by cells, change in the life cycle in ways that we did not fully realize before
.
" "Now we really need such big data to answer these questions.
.
"
(Biocom)
Original search:
Herman Pontzer et al.
Daily energy expenditure through the human life course.
Science, 2021 DOI: 10.
1126/science.
abe5017