It’s commonly believed that your metabolism slows down as you get older.

It seems to make sense: you might’ve put on some weight—especially during adulthood—and you might find it challenging to get back to an old weight.

Is metabolism to blame?

Metabolism is the sum of all chemical processes that occur within each of us to maintain life. Everything you do, from eating and sleeping to moving and growing, requires energy. The energy you use per day is called total daily energy expenditure.

As we age, our expenditure changes because of changes in our anatomy, behaviour and tissue metabolism.

In a sizeable study, Pontzer and colleagues (2021) identified four distinct metabolic life stages:

1. Neonates (0‒1 year old)—daily expenditure increases rapidly to ~50% above adult values at ~1 year
2. Childhood and adolescence (1‒20 years old)—expenditure decreases slowly to adult levels at ~20 years
3. Adulthood (20‒60 years old)—expenditure remains stable
4. Older adulthood (60+ years old)—expenditure decreases by ~0.7% per year.

Therefore, metabolism does appear to slow down as you age but much later than commonly believed. That is, metabolism tends to be stable during the ages of 20‒60 years and the decline that starts around the age of 60 years old is slow.

These study findings suggest that contrary to popular belief, weight gain during adulthood may not be simply due to slowed metabolism. It’s important to note that numerous other aspects of your life change within this time period that may contribute to weight gain; for example, more sedentary behaviour, less sports and exercise, new life stressors and responsibilities, different eating habits, and development of medical conditions.

For those who believe that their metabolism is a significant limiting factor, perhaps there’s some hope.