What's the deal with your metabolic age?

Many of us will remember a time in our lives when we could eat anything we wanted and gain little, if any, extra weight. Maybe for you, this was all the way up to your 20s or 30s. Maybe this period ended in your teens. Maybe this has never been you, and that’s normal.

This superpower comes down to the speed at which our bodies metabolise food, which is different for everyone.

If you've taken deep dives into internet fitness forums, you may have seen the term "metabolic age" come up more often than once. Science has known for a while that the timing of our metabolic life stage is usually incongruous with our chronological age.

Measuring your metabolic age is similar to measuring your body mass index (BMI) — there is a formula you can use that takes into account your actual age, height and weight and will give you an indication of your metabolic age. But is this a useful measuring tool? And how should it be used? 

What is metabolic age?

To understand metabolic age, we need to understand metabolism. Metabolism is the internal process by which the body burns calories [1].

Your metabolism works all day and all night, converting the fuel you’ve consumed into the energy your body needs to function. Your metabolism accomplishes 3 important tasks: converting food into energy; breaking down food into its building blocks for protein, lipid, and nucleic acid, and eliminating nitrogen wastes.

We know that we cannot blame a sluggish metabolism squarely on our age: in fact, age plays a relatively minor role in how the metabolism works [2].

Essentially, a fast metabolism burns calories at a quicker rate. Therefore, people with fast metabolisms can eat a lot and not gain as much weight. A slower metabolism burns fewer calories, which means more gets stored as fat in the body.

To figure out where you stand with your metabolism, you need to calculate your basal metabolic rate (or BMR). Your BMR can tell you what calories your body is capable of burning while at rest. Then, it's compared to other people of your age group — that's how you get your metabolic age.

What is my BMR?

Having a look at your BMR can be a useful form of measurement of a person's overall health and fitness. It should be used in conjunction with other tools such as BMI and under the guidance of a doctor or healthcare professional [3].

No 2 BMRs will be the same. Your BMR will be influenced by:

Body size

Larger bodies typically have a larger BMR because they have more metabolising tissue.

Body fat

Fat cells can cause a sluggish metabolism meaning the body will burn fewer calories than other tissues and organs.

Physical activity

Increased physical activity increases muscle mass and trains the body to burn calories faster [4].

Fad dieting or fasting

Eating too few calories encourages a slower metabolism to conserve energy. This is a leftover side-effect of our prehistoric ancestors, whose metabolisms would slow down to see us through famine and long winters when food was scarce.  

Age

Your metabolism will slow down as you age because of hormonal changes and a loss of muscle mass.

Sex

On average, men have a faster metabolism compared to women because they have larger bodies.

Hormones

Hormone imbalances will have an effect on your BMR. 

How to calculate your metabolic age

You can estimate your BMR, but calculating your real metabolic age is complex. In a recent study, metabolic age was assessed after fasting and factoring in:

• Body composition
• Waist circumference
• Resting blood pressure

The researchers used special software and a 5-day diet analysis on the participants. The calculation for relative metabolic age was to subtract chronological age from metabolic age [5].

But, in order to know your metabolic age, you must know your BMR. To get an idea, the most common formula is:

• For women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161
• For men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5

To get your relative metabolic age, you need data on other people your age. If you’re interested in determining your metabolic age, talk to your doctor, dietitian, personal trainer, or other fitness experts.

At what age does your metabolism start to slow down?

For years, the assumption has been that your metabolism is slowing as you age. But, recent studies are showing that this might not be true. 

A study that included 6,500 people from 29 countries shows that metabolism for both men and women really doesn’t significantly drop off until you reach the age of 60. The age range of participants in the study ranged from as young as 8 days to as old as 95 years [6].

Metabolism speed isn’t strictly related just to your chronological age: it is influenced by your weight, body size, composition and tissue development, overall health, lifestyles, cultural and ethnic backgrounds and even geographic location.

It is influenced by what biological sex you are, whether or not you’ve had children, what stressors are happening in your life and much more [6]. 

This is exactly the reason doctors use BMR to determine metabolic age because it rarely, if ever, lines up with your chronological age. Even then, the metabolic age measure should only ever be used as a ballpark figure to determine what you can do differently with your body. 

The rule of thumb is if your metabolic age is lower than your actual age, it's a good indicator that you need to improve your metabolic rate by improving your diet and increasing your physical activity. 

What your metabolic age says about your health

A good metabolic age should be roughly close to your age in real life. If you’re 40, a healthy, balanced metabolic age will range between 35-45. Your metabolic age might read as younger than your actual age and that is fine — as long as it's not too low.

What if my metabolic age is high?

A person who has a high level of muscle mass will burn more calories while resting than someone with a lower muscle mass. So the fitter, healthier, and stronger you are, the lower your metabolic age will be.

If your metabolic age is higher than your actual age, it's a good indicator that you need to improve your metabolic rate by improving your diet and increasing your physical activity.

All of this information is a lot to take in. What we know to be true, from the studies that have looked at metabolism from every angle, is that all people looking to lower their metabolic age need personalised medicine.

Existing evidence is shouting at us that weight loss is possible with tailored nutrition and medical care that works to suit all the very different bodies out there.  There is absolutely no one-size-fits-all approach to weight loss.

How to improve your metabolic age

Get enough sleep

Yes, that's right — not getting enough sleep can have serious impacts on your metabolic process.

If you're trying to improve the body's ability to stimulate metabolism, getting a consistent 8 hours of sleep a night is a great place to start. If you're having trouble winding down at night, or not feeling rested when you wake up, you may need to improve your sleep hygiene.

Strength training

More and more evidence is showing the benefits of strength training on your metabolism [7]. Acquiring lean muscle mass can help you burn more calories faster while you are at rest.

High-intensity workouts

HIIT training actually affects your body on a molecular level. It is proven time and time again to be the most effective workout to change your body composition for the better [8].

Nutritious foods

A healthy lifestyle plays a massive role in shaping your metabolism. But, it's not just about what you eat — how much of it you eat also plays a part. Foods high in protein, fibre and healthy fats mean you're less likely to be hungry following your meal, therefore less likely to reach for even more calories.

On the other hand, not eating enough food can impact energy storage and cause a slower metabolism, so we suggest staying away from crash diets. If you've noticed some signs of a slow metabolism, foods with good fats like avocado, nuts, seeds, oily fish, eggs and yoghurts will impact how full you feel.

It's probably best to limit the number of refined grains, and fatty and sugary foods like chips and sugary drinks you consume, as this will have the opposite effect and slow your metabolism down.

Try a medical weight loss program

Talking to a clinician or health coach about your BMR can help you get to the root cause of where you are at physically, therefore helping you make the necessary changes towards a healthier lifestyle that suits you.

Juniper’s Metabolic Reset Program can help you do just that.

Our program combines weight loss medication, health coaching and ongoing support to help you lose weight and keep it off. We prescribe a GLP-1 medication called Wegovy, which contains the active ingredient semaglutide.

Semaglutide is clinically proven to reduce your appetite and make you feel fuller for longer, while also reducing cravings by targeting the rewards centre in the brain. For long-term success, changing your eating and movement habits is also crucial, which is why we offer a comprehensive programme that includes 3 core pillars of lifestyle change with the assistance of our UK clinicians.

We can help you break habits that might be impacting your weight and help you hit your weight loss goals sooner.