Do you have a slow metabolism?
The term 'metabolism' gets thrown around a lot in the fitness community.
But I always wonder if people know what it means 🧐
So, I'm going to start by explaining what exactly it is - then we'll figure out if yours is fast, slow or somewhere in between.
Ready? Let's GO!
Metabolism - AKA your Netflix and chill calories
When people talk about metabolism, what they're really referring to is their metabolic rate.
The scientific term for this is your resting metabolic rate (RMR), which is the amount of energy (measured in calories) that your body needs to maintain vital life functions at rest 😴
Your RMR covers critical processes like breathing, blood circulation, controlling body temperature, cell growth and more!
A whopping 60% of the average person's total daily calorie burn is accounted for by their metabolism 🔥
That's a big piece of the pie!
Think of these as your Netflix and chill calories – you would burn them even if you stayed in bed all day watching your favourite shows 📺
The remaining 40% of your daily calorie burn comes from physical activity, which covers everything from exercise to fidgeting and maintaining your posture.
To lose weight, you need to create a calorie deficit, which means eating fewer calories than you expend each day 😶
If your body doesn't get the energy it needs to function from your diet, you force it to break down your body fat and use that for fuel instead ⚡️
Still with me?
Imagine we have two people dieting on the same number of calories and performing an equal amount of physical activity.
The person with the higher RMR will lose weight the quickest, as they will create a bigger calorie deficit than the other person.
In this example, the person with the higher RMR has the 'fastest' metabolism 🏃♂️
How to test your metabolism
You can test your RMR with a very high degree of accuracy by visiting the sports science department at your local university – which is what I did!
Here's a picture of me taking the test 👇
As you can see, they hooked me up to a big machine and measured:
How much oxygen I consumed, and
How much carbon dioxide I released over 20 minutes in a resting state.
I basically got to have a nap for 20-minutes! 🛌
They then plugged my results into an equation to calculate my average daily RMR 🤓
ANDDDD – drum roll for the result, please 🥁
My resting metabolic rate is 1,933 calories.
The cool thing is that you DON'T have to visit your local university to get a reasonable estimate of your RMR.
Instead, you can use one of several prediction equations that researchers have developed based on the relationship between RMR and more easily measured variables like your lean body mass, height, age and gender.
Here’s how my actual RMR compares with three of the most popular prediction equations 👇
My actual RMR = 1,933 calories
Katch McCardle equation = 1,967 calories
Harris Benedict equation = 1,978 calories
Mifflin St Jeor equation = 1,885 calories
As you can see, the equations got pretty close to my actual result, but this won't always be the case.
That's because they were all developed based on samples of people who aren't YOU.
So, take your result with a pinch of salt and think of it as a range – your RMR might be 10% higher or lower than whatever the equation tells you 🤷♂️
And while your RMR will be relatively stable from one day to the next, it can change over time ⏰
For example, weight gain or loss, ageing and changes in your health status, e.g. thyroid levels, can all cause your RMR to go up or down 📈📉
You can use this online calculator to estimate your RMR with the Harris-Benedict equation
(You’ll notice that the calculator says ‘BMR’, which stands for basal metabolic rate and is the same thing as RMR - there’s just a technical difference in how scientists measure them.)
How to know if your metabolism is fast or slow
The only way to find that out is to get your RMR tested in a lab and compare it to your results from several prediction equations.
If your actual RMR is lower than your results from the prediction equations, then your metabolic rate is slower than we'd expect for somebody of your age, gender and build.
If it comes back higher, then your metabolic rate is faster than we'd expect.
Ultimately, if you can maintain your weight with a calorie intake and an amount of exercise that you find sustainable – I'm guessing your metabolism is perfectly healthy 👍👍👍
JT – I struggle to lose weight, is it my metabolism?
I HAVE worked with clients where it's taken a lower number of calories than I'd expect for them to lose weight.
Which might be due to them having a slow metabolism.
But I can't rule out the possibility that they were eating more calories than they were reporting in their food diary 📝
If you're eating relatively close to your RMR and being active, but not losing weight, make sure you're properly tracking your calorie intake.
You also need to consider that you might have unrealistic expectations about your rate of progress.
Your weight might be dropping, just not as quick as you'd like! 😣
From experience, I've learned that losing 0.5-1% of your average bodyweight each week is a great result.
My final tip is to be as physically active as possible 🏋️♂️
Make time for 3-4 intense workouts a week and try your best to hit 10,000 steps a day.
Doing this will help you create the calorie deficit required for fat loss on the highest number of calories possible.