Metabolism slows down with age – truth or another myth?

Although the term “metabolism” in everyday speech is most often associated with gaining or losing weight, metabolism is actually something much more and more complex – more precisely, it encompasses all physiological processes and chemical reactions that take place in our body to survive. And while most of what we know about it is unlikely to change, or at least not any time soon, there are some truths about human metabolism that we’ve all believed in for a long time that might be wrong according to the latest knowledge.

This is evidenced by a new study involving as many as 82 co-authors and which brings together several quality studies from around the world published over a period of forty years – from 1980 until the last study published this year. Obviously this is a topic that is often researched, but what makes this study interesting is the fact that even researchers were surprised by the results of the same related to questions about when our metabolism is really speeding up and slowing down.

These results could surprise you, especially if you believe that your weight gain is solely due to years, or a slow metabolism that they brought you. I'm sorry, but I'm going to have to disappoint you – the main culprit seems to be hiding somewhere else.

Main features and conclusions of the study
The researchers collected data from 6,421 participants from 29 countries of all ages – from an 8-day-old newborn to the oldest 95-year-old participant. As many as 64% of the participants were women.

Metabolism can be presented as the level of total daily energy consumption, and part of which (along with physical activity and thermal effect of food) is basal metabolism, which is the minimum energy we need to survive. Many factors affect the level of basal metabolism throughout life, but what always remains is the fact that it accounts for most of the daily energy expenditure.

The study therefore identified four different stages of basal metabolic rate and total daily consumption:

  1. From birth to the first year
    Newborns have a level of metabolism, ie the total daily level of consumption, similar to adult metabolism (after adjusting body size), which means that the baby's metabolism is in line with the mother's metabolism.

But after a month, total daily consumption accelerates dramatically and reaches its peak around the first birthday when it reaches a metabolic rate 50% higher than adults.

  1. From the first to the twentieth year
    Although children and adolescents do grow like plants in the rain, it seems that once the change in weight is taken into account, their metabolism compared to newborns actually slows down. The same goes for puberty.
  2. From the twenties to the sixties
    This is the part that will probably surprise you even more than the previous one. Contrary to many beliefs, metabolism stabilizes after puberty and remains so until the age of sixty. Interestingly, this study refuted as many as three myths related to this forty-year period:

There is no difference between men and women once we adjust body size and lean body mass
There are no changes in menopause. Yes, even despite the change in the hormonal picture and the feeling of many women that for them every bite is simply “beautiful”, studies have not detected a real change in total daily energy expenditure, or metabolic rate
The same change does not occur in men of the same age

  1. From the sixties onwards
    Only here does the story change. After the age of 60, total daily energy consumption decreases by 0.7% per year, which means that if you live to be 95, your metabolic rate will be 20% lower than you were when you were 50. This change is visible even after adjusting for body size and lean body weight, which is known to decrease with age and that this reduction affects metabolism.

One of the reasons, researchers claim, is that with the loss of lean body mass, fewer calories per kilogram are consumed, and it is evident that organs that are large consumers of energy such as the brain and liver lose their appetite in later years.

The researchers of the mentioned study were surprised to find something that must have surprised you as you read this text – the level of metabolism in men and women remains constant between the ages of 20 and 60. And that suggests to us that if we notice extra pounds on our bodies every year, it may not be our metabolism but our habits of moving less and eating more than we did decades ago. Therefore, before blaming your age for being overweight, remember the good habits you may have put aside lately – especially adjusting your food intake to your body's needs.

If you immediately thought of your favorite calorie calculator keep in mind that estimating calorie needs is not that simple. Some people do have a metabolic rate higher or lower than average, even up to 25% in extreme cases, which is why it is important to understand the calculations only as a starting point, and then adjust food intake and activity level depending on the results. Anyway, there are many different ways to stay in shape – despite your age.

And that's really good news, isn't it?

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