Metabolism: Why does it slow down as we get older?

Metabolism: Why does it slow down as we get older?

Have you heard anyone say, ‘I have a slow metabolism’? Or ‘I can’t eat like I did when I was 20, my
metabolism isn’t as good anymore!’ We sure have!

So is it true, are we born with fast or slow metabolisms and does our metabolism slow down with
age? The article below tells you everything you need to know about your metabolism and how you
can optimise yours to support your health and fitness goals.

Firstly, what is your metabolism?

Your metabolism is a combination of chemical reactions that help keep your body alive. These include
your resting (or basal) metabolic rate (RMR/BMR), thermic effect of food (TEF), non-exercise activity
thermogenesis (NEAT), and exercise activity thermogenesis (EAT). All of these work together to determine your metabolic speed.

It is important to establish what all of these abbreviations stand for, so let’s cover this, to begin with.

Resting or basal metabolic rate (RMR/BMR)

Your metabolism if you were in a comatose state. Your BMR is the energy you burn every day whilst at rest.

Thermic effect of food (TEF)

This is the amount of energy your body burns whilst you are eating and digesting food. Remembering
that your food is made up of macronutrients (protein, carbohydrates, and fats), the most thermic macronutrient is protein. This means that protein uses more energy in comparison to carbohydrates
and fats) to break down the energy. This is why protein is important to consume in a balanced diet to
feed and optimise your metabolism. Don’t worry, we will cover this in more detail later on.

Non-exercise activity thermogenesis (NEAT)

This is the exercise or movement you are doing without thinking. Whether you pace around your home whilst talking on the phone, you walk to and from the station each day at work, or you make an effort to clean around the house; this all makes up your NEAT and varies day to day.

Exercise activity thermogenesis (EAT)

This is the exercise you are consciously participating in week to week. This could include a run on the weekend or a session with one of our MotivatePT trainers, your EAT is the energy you are burning during each of these sessions. So what kind of exercise is the best to support your metabolism? Don’t worry, we will cover this later on, so keep reading!

So, why is our metabolism something to think about?

Our metabolism is critical to how much energy we burn throughout the day and therefore how much energy we need to consume daily. This is why when people are undertaking a fat-loss phase, considering the factors that make up our metabolism is important to optimise the results we are wanting to achieve. The metabolism of someone who works in an office job from 9-5, walks for a maximum of 30 minutes per day and does pilates 3 times a week in comparison to a tradesperson who is moving all the time for their job and is strength training 4 times per week is vastly different and is why the energy needs of each individual (and the rate of which their metabolism is working) are so different.

Can someone be born with a slow metabolism?

Genetics do play a role when it comes to our metabolism, however often we need to look at the variety of factors that come into play when it comes to our metabolism. Do you have a history of dieting on really low calories in the past? Do you have little movement day to day due to your work? Are you a naturally stressed or anxious person? Do you have adequate protein in your diet? Do you have any medical or hormone concerns? All of these factors, including your family history, gender, age, and physical attributes, can impact your metabolism. It is important, however, to know that you CAN improve your metabolism and below we are going to give you some tips on how you can do it!

How can we improve our metabolism?

When we look at the chemical reactions above, we can see that a lot goes into how efficiently or inefficiently our metabolism is operating each day. The good news is, however, that we can change and improve our metabolism over time with some dietary and movement changes! Here are five of our top tips for improving your metabolism:


The yo-yo dieting needs to stop. This means spending more time eating at maintenance and allowing your body to feel like it isn’t going to be starved at any moment in time. The binge and restrict cycle (we are talking about the 1200-calorie diet to then going back to takeaways every night with a bottle of wine) is sending your body into a state of confusion! Your body is then holding onto your fat as a means to survive in case you decide to overly restrict again in the near future. If you are going to diet, ensure it is well-balanced and doesn’t overly restrict your body for an extended period.


There is a lot of hype around 10,000 steps per day, but this is a great way to encourage people to keep their movement regular and consistent each day in a bid to improve their NEAT. Whether it is even just a 30-minute walk a day or a cycle to and from work, the more you can increase your movement the more you will be burning each day.


Resistance training helps to build muscle, putting our body into an anabolic state. An anabolic state means that our body is burning energy to strengthen our muscles and bones. The more we can be in this state, the more energy our body is burning and therefore firing our metabolism.


Above we spoke about our TEF or thermic effect of feeding. To recap, this is essentially our body burning energy as we eat. Consuming more protein (which has the highest TEF of all macronutrients as mentioned above) means that our body is constantly burning energy to feed our muscles, in turn increasing the work of our metabolism over time.


It seems to be contradictory to the information above, however allowing our body to have time in a rest and digest state, away from the stressors of life, and focusing on adequate sleep is supportive in ensuring that we can regulate our blood sugar levels and manage our hunger hormones. This will, in turn, allow us to have a consistent and adequate food intake and support our body to efficiently keep our metabolism burning.

So why is all of this important when considering metabolism and age?

Considering the varying factors of metabolism and how we can improve them during all stages of life
is important, as listed above, and shouldn’t just be considered as we reach the middle of our life.
There are many things we can do to ensure our metabolism is as efficient as possible across most of
our life. Most research has highlighted that any reduction in metabolism as we age (which isn’t
drastic) is usually due to reductions in energy output! As discussed above, energy input and output is
a sliding scale and they work together to establish our metabolism. So, the more we can focus on
keeping up the habits and activities that have been listed above as we age will allow us to ensure that
our metabolic speed stays healthy and consistent for the majority of our life.

It is true, however, that our metabolism does start to decline as we age. By how much though? The
research is limited and there are mixed outcomes on when this occurs and by how much. In one of
the most recent studies on the subjects, the TDEE was monitored and by a large study group of 6,400
people of all ages, genders from 29 different countries. The study showed that our metabolism is at
the highest rate when we are aged 1 and declines until we are around 20 years old. After 20, the
study indicates that our metabolism plateaus until we turn 60 years of age, which is where a decline
was seen, however, it was by less than 1%.

Timothy Rhoads and Rozalyn Anderson commented that “the decline from age 60 is thought to reflect
a change in tissue-specific metabolism, the energy expended on maintenance” (link to article). This
shows the importance of our energy expenditure, which is our NEAT and EAT, again highlighting the
importance of exercise throughout our whole life.

self-care for mothers, taking care of yourself

So what should we do with this information?
The main thing to take away from this blog and the articles referenced above is that blaming age for
your declining metabolism is probably not as accurate as you may have thought. By ensuring that you
are spending enough time eating enough food to support your body’s daily needs, you are moving
regularly, you are focusing on resistance training, and you are looking after your body with rest, you
can maintain a healthy and efficient metabolism.
Instead of focusing on your age to create blame, focus on using the time to stay healthy, fit, and
strong to maintain an efficient metabolism for as long as you can!

Written By Paige: Female fitness expert at MotivatePT – Reps Level 3 Qualified / Pre & Post Natal

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