Metabolic Age: What Is It About and How Does It Impact Your Health?

Written by Taisiia Dobrozorova

Written by Taisiia Dobrozorova

Taisiia Dobrozorova is a nutrition and fitness writer at Unimeal and a healthy lifestyle devotee. She has accomplished several courses on health, nutrition, dietology.

on November 15, 2021

Nowadays, metabolic age has become a popular term in the world of health and nutrition. And this is not surprising. It has a lot to do with the level of your metabolism, thus, and well-being. This article will help you find out what your metabolic age is and how to improve it.

Have you ever wondered why some people look younger or older than their actual age is? And how to improve the condition of your body to look your best? 

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For maintaining good physical shape and health, calculating metabolic age and metabolism can be a sticking point. Scientists are still studying how useful this indicator is from a medical point of view. But for assessing changes in your body over a period of time, it is undoubtedly vital.

Metabolism¹A. Judge, M. S. Dodd. (2020, August 24). Metabolism. Essays in Biochemistry. DOI:10.1042/ebc20190041 is the processing of substances entering the human body. The metabolic rate is the rate at which the body burns calories. Metabolic rate depends on many factors: environment, exercise level, smoking, gender, body fat percentage.

Getting a little ahead, we can hint that metabolic rate, as you might have guessed, is the required part for measuring your metabolic age. More precisely, we will need your BMR or basal metabolic rate. So let's firstly figure out what it is and how we can measure it.

Basal metabolic rate - BMR

Basal metabolic rate (or BMR) is the number of calories that the human body burns at rest, that is, the energy expended to support all life processes, for instance:

• respiration
• blood circulation
• digesting food
• maintaining body temperature
• cell production

In a nutshell, BMR is the minimum number of energy your body needs to fulfill its most basic (basal) functions.

That means if you were to lie in bed all day, this would be enough for your body to function properly. BMR depends on your gender, height, weight, muscle mass, and a number of other factors.

What is the difference between BMR and RMR?

Some people often confuse BMR with RMR, which is almost no different from the first one, but not completely.

RMR, also known as Resting Energy Expenditure (REE), is the resting metabolic rate. It determines what amount of calories you need while having no loads and only light physical activities. Among these activities are:

• walking
• eating
• sweating and shivering 
• using the bathroom, etc.

So, the difference in calculating these two indicators will be in the state of the body (BMR requires complete rest, RMR, in turn, can be calculated after small physical exertion).

How to measure your BMR?

To determine your metabolic age, you first need to learn how to measure your BMR. There are several formulas you can use to measure your BMR.

Each of them includes key indicators: weight, height, age, and gender. This list also may be complemented by your level of activity, but more on that later.

The first and the most popular way of estimating your BMR is Harris-Benedict’s formula:

To estimate your BMR, you can also use the Mifflin St. Jeor formula, known since 2005.

They do not differ much, but Harris's formula is older and is more often taken as the basis for modern BMR calculators. Some nutritionists prefer to measure with both formulas for more accurate results, so the choice is yours.

Once you've estimated your BMR, multiply everything by your activity score. This gives you the final number of calories your body needs per day, not only for a state of rest but also for the level of activity your body is used to.

Light exercise: BMR * 1.375 = Total Calorie Need

Moderate exercise (3-5 days/wk): BMR * 1.55 = Total Calorie Need

Very active (6-7 days/wk): BMR * 1.725 = Total Calorie Need

Extra active (very active & physical job): BMR * 1.9 = Total Calorie Need

Congratulations, since you've calculated your total calorie requirement, you're halfway towards determining your metabolic age!

What is metabolic age (definition, meaning)?

Metabolic age is a term that has pervaded the fitness and nutritional fields in recent years. It is one of the touchstones that help people build a relationship between their metabolic rate and health indicators.

As in the case of body mass index (BMI), metabolic age has its own criteria. But neither one nor the other criterion is completely accurate due to the individual characteristics that need to be considered when assessing the final indicators. For example, a bodybuilder with a lot of muscle mass may have about the same metabolic age as someone with standard physical fitness.

Metabolic age vs. chronological age 

Chronological age is the number of years lived. It only shows the number in your passport but not the state of your body. If you want to know more about how your inner state of health coincides with the outer one, you should turn to metabolic age.

Metabolic age is the minimum number of calories your body needs to function at rest. Thus, this includes the calories you burn without exercising.

Suppose metabolic age coincides with the chronological age or lower. In that case, there is no need to worry, and if it is much higher, it is better to reconsider eating habits and add more physical activity.

Metabolic age vs. biological age

There are very few differences between biological and metabolic age. Researches²A. Moskalev. (2020, February 11). The Challenges of Estimating Biological Age. eLife. DOI:10.7554/eLife.54969 show that biological age is a statistic that can fluctuate owing to lifestyle and other health variables, including metabolism. And, vice versa, you usually calculate metabolic age based on metabolic rate only. When we talk about biological age, there are objectively more factors to consider.

All processes in the human body are of a phase, rhythmic nature - the lowest and highest body temperature, heart rate, blood pressure, synthesis of melatonin and cortisol and other hormones, the best coordination and attention, and so on. 

For instance, after 50 years, the structure of biorhythms becomes less stable, and the work of organs and systems becomes less coherent and reliable. Therefore, in determining the biological age, not only individual indicators are important, but also their relationship, ratio, and linkage to the time of day.

Some tests allow you to determine your biological age using a set of questions about your lifestyle. Then the specialist in the field can interpret the findings and make recommendations for lifestyle changes.

How to calculate your metabolic age

Once we've figured out how the concept of metabolic age appeared and its main differences from calendar and biological ages, we will go directly to its estimation.

Metabolic age is a measure that allows you to compare your metabolic rate with the average. For this reason, it will be enough for you to calculate the BMR (not forgetting the activity index) and compare it with the average indicators of your age and sex category. You will see which age is the best suit for your total calorie need and compare this number with your actual chronological age at the moment.

If your metabolic age is higher than the calendar age, it is worth taking measures to accelerate the metabolism of substances and lower the metabolic age. If the metabolic age is below the chronological age, this indicates good physical shape.

Disclaimer: despite the amount of input data, this calculation will be rather arbitrary. Basically, it's almost impossible to compare your personal BMR to others in your age group because so many factors Array³C. C. Douglas, J. C. Lawrence, N. C. Bush. (2007, April). Ability of the Harris Benedict Formula to Predict Energy Requirements Differs with Weight History and Ethnicity. Nutrition Research. DOI:10.1016/j.nutres.2007.01.016 how many calories you burn. Your body and shape, your ethnicity, your genetics can all play a role.

What can metabolic age tell you about your health?

Metabolic age and health are interrelated concepts. Scientists argue⁴R. Fernández-Verdejo, J. L. Moya-Osorio, E. Fuentes-López, et al. (2020, July 22). Metabolic Health and Its Association with Lifestyle Habits According to Nutritional Status in Chile: A Cross-Sectional Study from the National Health Survey 2016-2017. PLOS one. DOI:10.1371/journal.pone.0236451 that although there are predispositions to a metabolically unhealthy phenotype, most people are likely to have a healthy metabolism at birth. With age, this indicator can change, which we clearly observe in the state of human health.

With age, the metabolic rate decreases: the percentage of fat increases, the weight of muscle mass decreases, and physical activity. Fat cells consume less energy, and muscles are much more metabolically active. And every year, the number of calories burned decreases significantly.

After twenty years of age, the daily calorie consumption decreases by 150 kcal for every subsequent 10 years. And the body of a thirty-year-old person who is not physically active often consumes fatty foods, or fast food may have the metabolic rate of a fifty-year-old.

However, it is also worth remembering the factors that affect the metabolic rate and don’t depend on your nutrition. These include:

Age: muscle mass decreases with age, slowing down the metabolic rate;

Height: tall people have a higher figure;

Physique: the greater the percentage of muscle, the higher the metabolic rate, the more fat, the lower this level;

Temperature: high degree of the body speeds up the metabolism;

Stress: stress and illness increase calories burned;

Ambient temperature: very cold and very hot weather will speed up the metabolism;

Fasting: fasting, starvation, and malnutrition slow down⁵R. E. Patterson, G. A. Laughlin, D. D. Sears. (2015, April 6). Intermittent Fasting and Human Metabolic Health. Journal of the Academy of Nutrition and Dietetics. DOI:10.1016/j.jand.2015.02.018 the metabolism;

Hormones: some hormones can positively or negatively affect your metabolism;

Smoking: smoking increases energy expenditure;

Coffee: caffeine increases energy expenditure;

Sleep: the lowest metabolic rate a person has during sleep.

How to improve metabolic age 

A high metabolic age, which, moreover, does not coincide with the chronological age, is an alarming bell that signals the need to change your habits: eat right, exercise, spend more energy than consume. Here are a few more things to help improve your metabolic age:

To change your metabolic age, it's essential to follow these recommendations comprehensively. 

The bottom line

Metabolic age determines how young your body is on the inside. 

Basically, to calculate this indicator, you only need to know your BMR and compare it with the average results.

Yet, remember, calculating metabolic age is complex enough that your data may not be enough. For accurate results, you need to take into account your genetics, body composition, weight history, etc.

Whatever your metabolic age, you can always improve it by following a healthy diet and doing moderate exercise.

• Little/no exercise: BMR * 1.2 = Total Calorie Need

• Consume whole carbs.
• Increase your protein intake.
• Replace sugary carbonated drinks with water.
• Control calories.
• Work with a dietitian.
• Fill your plate with healthy foods (for a better result, use a meal planner.
• Eat 3 times a day and do not forget about snacks.
• Increase physical activity.
• Do strength training.
• Add HIITs (high-intensity interval training).
• Don't forget about stretching.
• Take a walk every night, at least for 15-20 minutes.
• Exclude stress factors.
• Set up your sleep routine.