They say age is just a number . But what if your body is actually older or younger than the number of candles on your birthday cake? That’s the idea behind metabolic age, which compares your body’s metabolism with that of other people in your age group. At least, that’s what’s promised. Currently, the concept of metabolic age is not well researched, but the term is gaining popularity in the fitness industry. Although a low metabolic age seems to indicate a lower risk of health problems, all of these claims should be taken with a grain of salt. What we do know is this: The things that seem to lower your metabolic age are generally healthy for you. So there’s no reason not to do them.
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Metabolic age: what is it?
Although metabolic age can be measured in several ways, it usually refers to how your basal metabolic rate (BMR) compares to the average BMR of people your age (lifetime). Metabolism and basal metabolic rate change with age.
So what is basal metabolic rate? It is the number of calories you need to maintain your basic life functions at rest without external influences. It does not take into account, for example, the extra energy you need to exercise or be physically active.
This value is slightly different from Resting Metabolic Rate (RMR), also called resting metabolic rate, which is the amount of energy your body burns at rest.
Why is metabolic age important?
Your metabolic age can be an indicator of your physical health. A metabolic age lower than your biological age indicates good health and a healthier, more active lifestyle, while a higher SWA indicates you may have health problems, according to a study in the May 2017 journalTransplantation (1).
Although much more research is needed, a small study of 19 people published in June 2019 inCurrent Developments in Nutrition(2) found a possible health advantage: metabolic age lower than life age was associated with lower blood pressure.
Why might your metabolic age be lower than your biological age?
First of all, basal metabolic rate depends on your gender, weight, height and age. So if you put on a few extra pounds for your height, this can lead to a higher metabolic age.
More advanced and accurate methods of measuring basal metabolic rate also take into account your body composition, which is the percentage of bone, fat, water and muscle. The biggest factor leading to higher SWA is most likely lower lean body mass relative to total body weight.
That’s because a higher ratio of lean body mass to fat mass often means you burn more calories at rest than someone of the same weight who has more fat, according to the Mayo Clinic.
And, of course, your diet and exercise habits affect your weight and body composition. For example, your metabolic age may be higher than your biological age if you don’t exercise regularly, eat habitually poorly and don’t manage stress well. This can lead to a loss of lean body tissue, an increase in fat, and an overall decline in health.
How to calculate metabolic age?
Wondering how to determine your metabolic age? There is currently no standardized method to determine it. Instead, various calculations and proprietary software are used, but none of them have been validated by research.
This means that if you want to calculate your metabolic age, you need access to data from other people who have the same biological age as you. But only some personal trainers, registered dietitians and other experts at medical or fitness centers have the technology to determine your metabolic age. If you’re curious, search online for providers in your area or give them a call.
These experts can calculate your metabolic age using a bioelectrical impedance scale. They stand or hold onto sensors that send a weak electrical current through your body that measures your body fat and lean body mass to calculate metabolic age.
There are also bioelectrical impedance scales you can buy online for home use, but their accuracy can vary.
If you have access to a metabolic age chart that shows your basal metabolic rate or the basal metabolic rate of other people in your age group, you can calculate your own metabolic rate. You can use several different formulas to do this:
1. the Mifflin-St.Jeor formula.
The Mifflin-St.Jeor formula for calculating basal metabolic rate is derived from the Harris-Benedict formula, as published in February 1990 in The American Journal of Clinical Nutrition(3).
For women: (10 × body weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161.
For men: (10 × body weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Let’s say you are a woman, 30 years old, 68 kg and 152.4 cm. Your basal metabolic rate would then be 1321.5. Remember, this is an estimate of the calories your body burns performing basic functions such as breathing and circulating blood, without exercise or physical activity.
Tip: Manual calculations are not 100 percent accurate. Absolutely accurate basal metabolic rate calculations require sophisticated equipment used in a tightly controlled testing environment.
2. the Katch-McArdle formula.
This formula uses lean body weight to calculate basal metabolic rate. You must know your body fat percentage to determine your basal metabolic rate using this formula. If you do not have this information, you should use the Mifflin-St. Jeor formula.
Fat-free body mass = total body weight (in kg) – body fat (in kg).
Katch-McArdle formula: 370 + (21.6 x fat-free body mass in kg)
For example: a person with a body weight of 84 kilograms and 10 percent body fat has a lean body mass of 75.6 kg. Insert these numbers and you will find that this person has a basal metabolic rate of about 2001.96 calories per day.
3. the Cunningham formula
If you are wondering how to calculate your resting metabolic rate (RMR), the Cunningham formula will help you. It uses lean body mass to provide a better measure of daily calorie expenditure than the Katch-McArdle formula, which is why it is also used as the RMR formula.
However, according to a study published in September 2013 in the journalTopics in Clinical Nutrition(4), it may overestimate the actual RMR value.
Cunningham formula: 500 + (22 x lean body mass in kg).
For the 84 kg person mentioned above, this formula gives an RMR value of 2163.2 calories per day.
How can you reduce your metabolic age?
If you want to reduce your metabolic age, you should pay attention to the following healthy lifestyle factors:
1. be active
Fat-free body mass is an important factor for metabolic age. In order to build muscles and gain fat-free body mass, you should do strength training. If you keep active in general, you can maintain your weight and lower your metabolic age.
2. eat enough protein
Protein supports muscle growth. A diet rich in protein will help you build muscle, especially if you are trying to lose weight at the same time. It is recommended that you consume about 1.3 grams of protein per kilogram of your body weight every day. So if you weigh 60 kg, multiply that by 1.3, and voila: you should be eating about 78 g of protein every day.
3. make sleep priority No. 1
At least seven hours of sleep per night is essential to achieve a healthy basal metabolic rate, recover from exercise, digest food well and get stronger.
4. manage stress
When we don’t find a way to properly manage stress, we sleep poorly, skip workouts, opt for fast and convenient foods that often make us feel worse later, and wreck our bodies. All of this can increase metabolic age.
5. Consider a plant-based diet.
According to the study inCurrent Developments in Nutrition(2), a plant-based diet is associated with lower metabolic age compared to biological age.
Your metabolic age provides insight into how your basal metabolic rate compares to others your age. A low SWA seems to indicate a healthier lifestyle and may mean you are at lower risk for certain health conditions. However, more research is needed to determine the best method for calculating metabolic age and its exact meaning.
1) Study in the journal Transplantation: May 2017.
2) Study in Current Developments in Nutrition.
3) Mifflin-St.Jeor formula / The American Journal of Clinical Nutrition, February 1990.
4) Study in the journal Topics in Clinical Nutrition.