Are You Older than Your Body: What is Metabolic Age?

It’s said to be rude to ask someone their age, but what about the age of your metabolism?

Although you may have been blowing your candles out on the same day for many years, your age on a calendar might not be the same “age” as the metabolic function of your body.

Let’s take a deep dive into the concept of metabolic age.

What is Metabolic Age?

Metabolic age is how your BMR (basal metabolic rate) stacks up compared to other people of your chronological age.

There are currently few peer-reviewed studies on the concept. Metabolic age is used more as a benchmark in the fitness community rather than the scientific one.

That being said, it does derive from scientifically studied concepts like BMR (basal metabolic rate). We’ll learn more about this concept later.

First, let’s get to know how metabolism works in your body and what factors allow your metabolism to thrive or suffer.

What is Your Metabolism?

Although many people like to throw around the term “metabolism” as a rough stand-in for “calorie-burning capacity,” it’s not really accurate, however, it is a component.

Metabolism is not really a “thing” like a specific organ inside the body.

Simply put, metabolism refers to a series of processes and reactions that take place inside your body. It lives in each of your cells to help keep your body functioning and alive.

The main functions of metabolism are:

• Converting food energy to energy that is available to power your cells
• Creating protein or other building blocks for your body
• Eliminating metabolic waste

So in a sense, what your metabolism does is repurpose the calories you consume, directing them towards fuelling and creating the building blocks that your body needs to function.

Although it’s an area of interest for many researchers, scientists still have a lot to learn about the processes of metabolism and why it affects people so differently.

For example, do you have a friend who is the same height, weight, and age as you, yet seems to be able to eat whatever they want and not gain a pound? In fact, they may even lose weight without trying.

On the other hand, do you know someone who, no matter what they do, can’t seem to shed weight, despite a seemingly perfect diet and hours in the gym every day?

Maybe you yourself are in one of these categories.

The fact is, we don’t exactly know how dramatically each component that makes you impacts the body’s metabolism.

That being said, these are a few elements that we commonly look at when discussing metabolism that are solid forecasters of how your metabolism will operate.

What Factors Affect Your Metabolism?

Age

The study of aging has long been linked with understanding metabolic processes.

Basically, we know that most people’s metabolism tends to slow with age.

Some people seem to be blessed with healthier metabolic processes that can keep them going for longer. Research has found that centenarians (people over 100 years old) tend to have better insulin sensitivity than control groups younger than them.

Insulin is associated with controlling your blood sugar (if you’re too insulin-resistant you can develop type 2 diabetes).

Generally, however, most people’s metabolism slows down with age. Current research indicates that this is most likely due to loss of muscle mass (more on this later).

Because older people tend to be less muscular than younger people, their metabolic processes slow down.

If you’ve ever heard a doctor or physiotherapist mention the importance of keeping muscle on to older folks, helping them keep healthy metabolism going as long as possible is likely one of the factors they’re on the lookout for.

Gender

Women are usually physically lighter and smaller, hold more body fat, and generally have lower metabolic rates than men.

We see this come into play a lot in the different ways that women’s bodies vs. men’s deal with fluctuating temperatures.

Because of having a lower metabolism, many women tend to get cold more quickly than men. This is because muscle helps to circulate blood better than fat. Men have a relatively higher amount of muscle per body weight, while women have higher fat.

Evidence indicates that women’s proportionally slower metabolisms than men don’t allow as much heat to get to their extremities, hence causing a cold feeling.

Muscle vs. Fat

Both body fat and lean muscle can impact how your metabolism works.

If you’re a highly muscular person, able to crank out 500 push-ups a day, you may generally have higher or faster metabolic rates than those with excess body fat. Why?

More muscle usually means more exercise. In this case, you’ll have a higher basal metabolic rate.

Building muscle can be another contributing factor that increases your insulin sensitivity, meaning your body processes glucose (sugar) better and you are at less risk of diabetes.

Hormones

Current scientific research indicates that hormones like leptin, insulin, and sex hormones all have a role to play in your metabolic functions.

Physical Activity

Physical activity is one of the most important tools for regulating your metabolism.

Even if you don’t exercise regularly, even a single “accute” bout of exercise can influence the metabolism.

If you’re a workout devotee, however, your regular exercise patterns force your metabolism to make chronic adaptations over time the more you hit the gym.

Getting regular exercise lessens your risk of metabolic diseases, including:

• Non-alcoholic fatty liver disease
• Type 2 diabetes

What is Basal Metabolic Rate?

Basal metabolic rate or BMR is the baseline number of calories you’d need to sustain the daily functions of your body if you did no exercise.

This includes processes like breathing, brain function, circulation, body temperature, and producing cells.

If you were totally sedentary, this is the amount of calories you’d need to consume to keep yourself alive.

But we all know you’re not (duh, you’re here reading a fitness blog about how to work out and better yourself in the gym). So what other factors go into how your metabolism works?

What is the Resting Metabolic Rate?

Resting metabolic rate or RMR expands slightly beyond the basic processes of BMR but not much.

Here, we include a few additional considerations like:

• Eating
• Light activity
• Short walks
• Stretching

Basically, think about your BMR as being your metabolic rate at the time when you wake up, vs. RMR would be a very slow day at work.

Both of these measurements can come into play when it comes to calculating your overall “metabolism.”

Generally, your BMR will be slightly lower than your RMR.

Metabolic Age Calculator

To calculate your metabolic age, first, you’ll need to know your BMR. Here’s a handy dandy calculator for that.

There are several commonly used formulas to calculate your approximate BMR.

One of the most common BMR calculation tools is this formula. This is called the Mifflin St. Jeor equation:

• Men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5.
• Women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161

Plug your stats in and see what you come up with.

Calculating your metabolic age means you’ll need to compare your BMR to other people of your age and gender.

Next, you’ll have to use a simple chart to get a rough estimate of your metabolic age. To do this, you’ll need access to a database of the BMR calculations of other people around your age.

If you want to access these records, talk to a qualified health and fitness professional who works with data and they may be able to provide insight for you.

An online metabolic age calculator can give you a rough idea of your metabolic age, based on the data compiled by the website that hosts the calculator.

That being said, this would only give you a small sample of age data. It can be eye-opening to compare yourself to these samples, but they may not give you much insight into what this means for your body or how you can realistically improve your metabolic health.

Metabolic age is not considered an exact science yet. Most research will need to be done in the domain for metabolic age to be a significant metric on how good or bad your health is.

How Can I Lose Weight With a Slow Metabolism?

No matter what your metabolic age may be, a higher metabolism or high BMR means you most likely have a faster metabolism. You’ll need to take in more calories per day to maintain or increase your weight.

Meanwhile, a lower BMR indicates a low or slow metabolism. This means your body is not able to burn calories as quickly and you may have a higher tendency to store or put on excess weight.

How Can I Improve My Metabolism?

More Exercise

More activity will increase both your BMR and your RMR. In fact, many leaner people tend to move around a lot.

Research from Sports and Active Living addresses a principle called “the fidget factor.” They found that slim people, compared to people with obesity tended to fidget or move around 2.25x more than obese people.

This activity was outside their regular workouts but seemed to have an impact on their metabolism.

Weight Training

Upping your lean muscle mass through weight training can be a great way to burn more calories and bump up a slow metabolism.

Get Regular Sleep

For all processes of the body, clean sleep is necessary. During deep sleep, your body repairs all its cells. For your cellular processes to function properly, ensuring good rest is necessary.

Whether you nap after a workout or at night, try to make sure you’re getting either a full sleep cycle or proper REM sleep. Around 8 hours of sleep is healthy for most adults.

Eat Protein

Lean protein is one of the best ways to build your muscles and we know muscle can be helpful to increasing your metabolism.

Aim to eat at least 1.4- 2.2 g of protein per kg of body weight to improve your muscle mass.

Lean protein sources can include:

• Salmon or tuna
• Chicken or turkey
• Lean ground beef
• Tofu
• Nuts and seeds
• Greek yogurt

It’s a good idea to speak to a nutritionist or registered dietitian if you have concerns about your protein intake.

If you’re getting too little dietary protein, consider supplementing with protein powder if your doctor recommends it. Creatine can also help you fuel your workouts too.

For some additional information on protein powders, creatine, and other supplements we’ve got you covered:

• Creatine Monohydrate vs. Micronized
• Can I Take Creatine Before Bed

The Takeaway

Metabolic age is an emerging concept, mostly considered in fitness communities to determine how healthy you are compared to other people your age.

It’s calculated by ranking your BMR (basal metabolic rate) on a chart up against others of your age and gender to see how you stack up.

To get a real estimate of your metabolic age, you’d have to speak with a healthcare profession with access to data on people’s BMRs.

Although there are online calculators that can give you a rough estimate, their data banks are at the mercy of only the other users who have taken online metabolic age tests, so it’s not necessarily a representative sample.

Take any metabolic age calculators you see online with a grain of salt! That being said, knowing your BMR gives you a good idea of how many baseline calories your body needs to operate.

Getting to know how many calories you’re burning in your workouts and how many calories you eat each day can give you a better understanding of what kind of fuel your body needs, how you process calories in and calories out, and what adjustments you may need to make if you’re looking to lose fat and gain muscle.

If you’re making any drastic changes to calorie consumption or burn via exercise, it’s a good idea to consult with your doctor or a fitness professional.

They can help guide you in the right direction so your metabolic health stays the best it can be.

How do You Exercise for a Better Metabolism?

Remember to prioritize aerobic exercises to get your heart rate up if you want to ensure the health of your metabolism long term. Lift weights regularly and you should see a lower body fat percentage with a more efficient metabolism. Be sure to target different muscle groups equally in your workouts.

Keeping your activity levels on track has many metabolic benefits too, especially for older adults. Make sure you are eating healthy diet with enough grams of protein. It's a good idea if you want to increase muscle mass. Essential amino acids are a key part of building healthy muscles.

To up your calorie intake, you may also want to investigate supplementing with creatine or protein powder. Fat burners, whether or not you work out, can be an option too if you find you store excess fat easily. If you have any existing health conditions, speak to a medical professional.

They can let you know if you are likely to see health benefits from adding a supplement to your routine.

References:

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Levine J. A. (2023). The Fidget Factor and the obesity paradox. How small movements have a big impact. Frontiers in sports and active living, 5, 1122938. https://doi.org/10.3389/fspor.2023.1122938

Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American journal of clinical nutrition, 51(2), 241–247. https://doi.org/10.1093/ajcn/51.2.241

Palmer, A. K., & Jensen, M. D. (2022). Metabolic changes in aging humans: current evidence and therapeutic strategies. The Journal of clinical investigation, 132(16), e158451. https://doi.org/10.1172/JCI158451

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Yang, L., Zhao, S., Gao, S., Zhang, H., Arens, E., & Zhai, Y. (2021). Gender differences in metabolic rates and thermal comfort in sedentary young males and females at various temperatures. Energy and Buildings, 111360. https://doi.org/10.1016/j.enbuild.2021.111360