Can We Blame Weight Gain on Our Metabolism As We Age?

Can we blame weight gain on our metabolism as we age?

Let’s start by briefly touching on what our metabolism actually is.

Put simply, metabolism refers to the chemical (metabolic) processes that take place in your body to maintain normal functioning and sustaining of life. It’s the use of energy in the cells inside of your body that support growth and repair of tissues, day to day maintenance of function, digestion, breathing, circulation and much more. 

Your brain, for example, is very metabolically hungry. The neurons in the brain take up around 75% of your metabolic needs to maintain healthy cognitive function. 

You may be familiar with the term ‘Basal Metabolic Rate (BMR)’. Essentially, this refers to the number of calories your body burns to maintain life and enable the function of organs such as the brain. This number will usually take up the majority of your daily energy expenditure. For most people, it’s around 60-70% of your total calories burned each day.

Is metabolism the real culprit?

With the fundamentals covered, let’s explore whether your metabolism is really the culprit when struggling to maintain a healthy weight in midlife!

People of all ages struggle to maintain a healthy weight. This could be due to a range of factors such as: overeating, a lack of exercise, and even genetics to a degree. You’ve probably heard the phrase “I just have  slow metabolism” thrown around before, but how accurate is this claim?

Let’s explore it!

A recent in-depth analysis of how age and body size affects metabolic rate appears to have debunked the myth of metabolic slowdown in middle age and has indicated that the weight gain many people in their 40s and 50s experience is primarily due to muscle loss and inactivity.

The study analysed over 6,500 people from 29 different countries, ranging from participants aged a week old, all the way up to 95-years old. As expected, the study found that your metabolism skyrockets as a young child, burning 50% more energy for your size due to the activity of cells during growth and development.

Interestingly, they found that metabolism stays high throughout childhood then decreases and flattens out to a ‘typical’ adult rate around 20 years old.

The most surprising finding from this study however was the stability of our metabolism through adulthood.

From the ages of 20-60, they found that daily energy expenditure remained stable, with no slowdown in metabolism through middle age or menopause. It was only around 60-years old that they began to see a reduction in metabolic expenditure by around 0.7% per year. This suggests that 90-year olds require around 25% fewer calories each day than somebody of a similar size 30+ years younger.

So what does this mean in practice?

This piece of research suggests that the midlife weight gain and the struggle many people face to keep body fat off around their 40s and 50s comes down to a range of  mostly preventable reasons. 

Factors including muscle loss, diet choices and inactivity are the main reasons for this weight gain. This would indicate that a “slow metabolism” is no longer a key player, nor viable culprit. Instead, unhealthy decision making and a negative energy balance is. 

The study found that the best predictor of energy expenditure is fat free mass (muscle and organs) and that a decrease in muscle mass compounds the decline in metabolic expenditure in older age. 

When we pair this with what we know about muscle and strength loss (sarcopenia), it becomes even clearer that holding onto muscle mass and maintaining a good level of strength as we approach our 40s and beyond is extremely important.

However, to caveat, it’s important to be aware that this isn’t the full picture. After 60 years old, our cells do slow down, along with many other complex physiological changes that occur with old age – all playing a role in metabolic activity.

So what can we do?

It’s not all doom and gloom. You can maintain a high metabolic rate and combat this inevitable metabolic slowdown before your 60s by keeping your metabolism firing on all cylinders and ensuring your muscle mass stays high with regular physical activity. 

It’s recommended that you perform both aerobic, resistance and strength exercises on a regular basis, along with a balanced diet, adequate protein and healthy lifestyle choices. 

I hope you found this article insightful! I’d love to know about your experiences with a slowing metabolism - let me know over on Instagram and I look forward to hearing from you! @olliethompsonhealth

Study mentioned:

Metabolism changes with age, just not when you might think (2021). Available at: https://www.sciencedaily.com/releases/2021/08/210812145028.htm