👴 Metabolic Age: What It Is, How It’s Measured, and Why It Can Be A Brilliant Motivator After 40+

Frank Sinclair
Sep 2
3 min read

Ever had one of those moments where you feel a bit smug about your fitness? I did recently. I hopped on a body composition scale, waited for the whirring and beeping to finish, and out popped the result:

👉 Metabolic Age: 25.

Now, considering I’m about to turn 40, that’s a solid 15 years younger than the candles on my next birthday cake. Cue me walking around the house for the rest of the day like a peacock, chest puffed out, reminding anyone who’d listen that apparently my metabolism hasn’t aged a day since my twenties. My wife was not impressed, but I was absolutely chuffed.

But what actually is metabolic age, and why might it be the perfect bit of motivation you need if you’re over 40? Let’s dig in.

What is Metabolic Age?

Metabolic age is basically your body’s way of saying: “Yo, here’s how old your metabolism looks compared to the rest of the population.”

It’s worked out by comparing your Basal Metabolic Rate (BMR) - that’s the number of calories your body burns just to stay alive (breathing, circulating blood, keeping your organs ticking etc) to the average BMR of people in different age groups.

If your metabolic age comes out younger than your actual age, it means your body is burning energy more efficiently than the average person your age. If it comes out older, it’s a nudge that maybe your muscle mass, activity levels, or nutrition habits need a little TLC.

How Is It Measured?

Most commonly, it’s done on a bioelectrical impedance analysis (BIA) scale - like the ones made by Tanita. These clever scales send a teeny, harmless electrical signal through your body to estimate:

Your muscle mass
Your body fat percentage
Your water levels
Your bone density

From there, the scale estimates your BMR and compares it against reference data for different age groups. Out pops your “metabolic age.”

It’s not a perfect science: hydration, recent meals, and even how warm the room is can nudge the numbers but as a general indicator and a source of motivation, it’s pretty brilliant.

Why It Matters More After 40

Once we hit our forties, the natural trend for most people is:

Muscle mass starts to decline (unless you actively train it).
Metabolism slows down.
Energy levels dip.
And those “just looking at a biscuit makes me gain weight” jokes start feeling a bit too real

That’s why seeing a metabolic age that’s younger than your actual years can be such a boost. It’s proof that what you’re doing is working, and a reminder that you’re not “too old” to be fit, strong, and full of energy.

And if your metabolic age comes out older? Don’t panic, it’s not a life sentence. It’s simply a signal that building muscle, improving your nutrition, and moving more can literally turn back your body’s clock.

My Takeaway

For me, seeing “Metabolic Age: 25” wasn’t just a nice ego stroke (though let’s be honest, I milked it for all it was worth). It was a reminder that fitness is about more than scales and waist sizes, it’s about how your body is actually functioning under the bonnet.

So whether yours comes out higher, lower, or bang on your birthday candles, take it as feedback, not a verdict. And if you need a laugh (or a reality check), tune into the podcast episode we just recorded where we dive deep into this exact topic.

✅ Bottom line: Metabolic age isn’t gospel truth, but it can be a powerful motivator , especially after 40, when looking after your muscle mass and metabolism matters more than ever.

And hey, if you score younger than your actual age, you’ve got my full permission to brag about it… just don’t expect your family to be as impressed as you are.

Good luck!

FRANK

your Personal Trainer / Young Whipper Snapper