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We hear about basal metabolism all the time. But do you know what it actually is? What does it mean when someone tells you that your basal metabolic rate is 1300 kcal? This number tells you what the minimum amount of energy is that your body needs. However, one important question arises. Is it enough for you? Today we will answer this together and in doing so we will also reveal, for example, whether you can speed it up.
What is basal metabolism?
Most of you have heard of it, but not everyone knows what it’s all about. Basal metabolic rate, also known as BMR, can be thought of as the energy the body needs for its “maintenance mode”. Practically, it’s the amount of calories that are needed to survive, as it uses this energy for the function of its essential organs. The body burns so much energy just by basic vital functions such as breathing or pumping of the heart.
You might be surprised how many calories you need just for your body to function properly. For the average person who is moderately active, BMR accounts for up to roughly 50-65% of total daily energy expenditure. For example, with a caloric requirement of 2000 kcal, as much as 1300 kcal can easily represent basal metabolic rate. Therefore, remember that even if you are not currently exercising and having a lazy day, your body naturally demands energy and that’s okay. [5]
Why do you actually need to know the value of your BMR, you ask? What will you use this information for? Practically, in everyday life, it’s just an interesting fact that certainly won’t do you any harm to be aware of. However, it is of more use to you when you need to calculate your energy intake. Whether you want to lose weight or put on muscle, this journey should ideally start with calculating your optimal caloric intake. And the first step to that is figuring out just what your basal metabolic rate is.
What is the difference between basal and resting metabolism?
Before we delve into the other secrets of basal metabolism, we need to be clear about one thing. Basal metabolism is not resting metabolic rate (RMR). While it’s common to confuse these terms, it’s worth knowing the difference. Both figures speak to the amount of energy the body puts out when it is at rest. The difference, however, lies in what conditions are currently affecting the body.
Basal metabolism is the expenditure of energy at maximum rest. The condition is that when measuring it, a person must be lying down, must have been fasting for at least 10 hours, be awake for a while, and be in a dark, temperature-controlled room. The basal metabolic rate can practically only be obtained under controlled laboratory conditions. [5,6]
Resting metabolic rate, known by the acronym RMR, is simply the amount of energy burned during times of minimal activity. You can think of RMR as the energy you expend when you’re cooped up in your house all day, lying on the couch in front of the TV and occasionally walking into the other room. This makes the RMR higher than the BMR, by roughly 10%.[5]
So in reality, it looks like we are talking about basal metabolism, but in reality it is more like resting metabolism.
Is basal metabolic rate the same as total daily caloric expenditure?
It is common for some to start calculating their ideal daily caloric intake and end up finding out their basal (resting) metabolic rate. Then, for example, with a result of 1400 kcal, they try to eat exactly that amount of calories each day in the good faith that they are doing the best for themselves. However, you already know that this is not sufficient. A person with a BMR/RMR of 1400 kcal would only need those calories if they were lounging around at home all day doing almost nothing.
However, as soon as they get dressed and walk just a few minutes to the store, for example, their energy needs increase. Not to mention that eating and digesting food itself consumes calories. To sum it up, whether you play sports regularly or are only minimally active, the amount of calories just at the level of basal metabolism is not enough for your body. In fact, the other activities you engage in on a daily basis increase your total energy expenditure.
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What accounts for the total daily caloric expenditure?
You can think of the Total Daily Energy Expenditure (TDEE) as an honest-to-goodness hamburger with several layers of goodness. Its base is meat – in this case, basal (resting) metabolism. However, a complete hamburger also has vegetables, cheese, sauce and other ingredients in it. Similarly, the total energy intake. To be complete, it is not enough to include only the energy needed for basic life functions. It also includes calories burned in other activities.
What does the total daily energy expenditure consist of?
- Basal metabolic rate (BMR) is the amount of energy required to maintain the body’s basic functions. However, it is the amount of energy that the body would expend only under maximally controlled conditions.
- Resting Metabolic Rate (RMR) is actually the basal metabolic rate increased by 10% and is the energy your body uses at maximum rest under normal resting conditions at home. It normally accounts for roughly 60 – 75% of the total calories burned per day. [1]
- The Thermic Effect of Food (TEF) are the calories your body uses to digest food. It typically represents about 10% of the total energy expenditure of a normal mixed diet. For example, if you burn 2,000 kcal per day, about 200 kcal of that is used just to process the food you eat. As a point of interest, protein has the highest TEF of all macronutrients, at around 20-30%. [2]
- The thermic effect of normal daily activities (NEAT – Non-exercise Activity Thermogenesis) is the energy expended during everyday activities. This includes walking to work, getting dressed, cleaning, etc.
- Exercise Activity Thermogenesis (EAT) is the calories burned during focused physical activity. This includes the energy expended during workouts and sports.
It is the last two components of energy expenditure – NEAT and EAT – that can be influenced the most. Depending on how much you move on a daily basis, they can make up 20% or even 50% of your total daily energy expenditure. This is useful to know, for example, when you want to control your weight or lose weight – especially the amount of physical activity will influence how much energy your body burns.
How is basal metabolic rate calculated?
Want to know how much energy your body needs? Then you need to start by calculating your basal (resting) metabolism. You can calculate it yourself, you just need a calculator and your height, weight and age. Then all you have to do is choose one of the available equations to calculate your BMR and you’re ready to do the math.
Which equations are most commonly used?
1. Harris – Benedict equation
This equation is the most widely known and used, despite the fact that it was created more than 100 years ago, in 1918. It has since been modified once in 1984 and this version is still in use today. [5]
Just like the other formulas, this one also takes gender into account and therefore the calculation is different for men and women.
- Harris-Benedict equation for women: BMR = (9.247 x weight in kg) + (3.098 x height in cm) – (4.33 x age) + 447.593
- Harris-Benedict equation for men: BMR = (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age) + 88.362
Now we will practically show how this formula is used to calculate the basal metabolic rate of a 30-year-old woman with a height of 170 cm and a weight of 70 kg.
- BMR = (9.247 x 70 kg) + (3.098 x 170 cm) – (4.33 x 30 years) + 447.593 = 1491.643 kcal
According to the Harris-Benedict equation, this woman requires about 1,492 calories just to keep her body functional and healthy.
2. Mifflin-St. Jeore equation
The Mifflin-St. George equation, although not as well known as the previous calculation, is now considered more accurate. Interestingly, it is also a revised Harris-Benedict equation. Mifflin-St Jeor modified it in 1990 and the calculation looks as follows. [5]
- Mifflin-St Jeore equation for women: BMR = (9.99 x weight in kg) + (6.25 x height in cm) – (4.92 x age) – 161
- Mifflin-St Jeore equation for men: BMR = (9.99 x weight in kg) + (6.25 x height in cm) – (4.92 x age) + 5
According to this equation, what is the basal metabolic rate of the same 30-year-old woman with 170 cm and 70 kg?
- BMR = (9.99 x 70 kg) + (6.25 x 170 cm) – (4.92 x 30 years) – 161 = 1453.2 kcal
As you can see, the result is a few calories less than the previous equation. It is this deviation that makes the Mifflin-St. Jeore equation slightly more accurate than the Harris-Benedict equation.
What other formulas are you familiar with?
The previous two formulas are not the only ones you can use to calculate basal metabolic rate. Experts have come up with other formulas as well, and the most well-known of these are the following.
For women | For men | |
|---|---|---|
| Katch-McArdle equation (2006) | BMR = 370 + 21.6 x active body weight (FFM – Fat Free Mass) | the equation below is used |
| as developed by FAO/WHO (1985)* | BMR = (8.7 x weight in kg) + 829 | BMR = (11.6 x weight in kg) + 879 |
| Owen Equation (1986) | BMR = 795 + (7.18 x weight in kg) | BMR = 879 + (10.2 x weight in kg) |
*for people aged 30 – 60 years
Which equation should you choose?
When you want to calculate your basal metabolic rate, it can be quite a dilemma which equation to follow. Although the Harris-Benedict equation is the most well-known, experts say it overestimates basal metabolism by roughly 5%. Mifflin-St. Jeore’s formula is slightly more accurate.
An option is also to use several equations and compare or average their results with each other. In the end, there will not be that much difference between the values. As you saw above, the resulting BMR value differed by only a few tens of kcal between the two most well-known equations.
But if you’d like to save yourself the hassle of calculating, comparing and averaging, we can make it easier for you. You can help yourself with our online BMR calculator, which figures out your basal metabolic rate for you.
Can basal metabolic rate be measured?
While most calculate their basal metabolic rate using equations, there are special devices that can measure it. This measurement takes place in laboratory conditions and is, of course, far more accurate than a calculation. The result can vary by about 10-20%. However, this is very individual, depending on age, gender and other factors. [3]
- Think of indirect calorimetry as a kind of breath test. It analyses the amount of oxygen inhaled and carbon dioxide exhaled to determine how much energy the body uses for its basic functions.
- Direct calorimetry measures the total heat produced by the body. The measurement takes place in a so-called calorimetric chamber, where the environmental conditions are perfectly adjusted and controlled. This method is only used in specialised research centres. [5]
What affects basal metabolic rate?
We’ve already mentioned that if you want to increase your overall energy expenditure, the easiest way to do it is to increase the amount of daily exercise you do. But don’t get the wrong idea – basal metabolic rate can be influenced too. Plus, other factors have an effect on it, which makes it a little different for everyone.
1. Age
Also, do you think that older people find it harder to shed extra kilos because of a slower metabolism? It’s not so clear-cut, but there is some truth to it. Basal metabolism typically really slows down as we age. This is mainly related to a decline in muscle mass. This is because it is more energy-intensive and if you have less of it, this has an impact on the decrease in basal metabolic rate. The surprise, however, may be that BMR doesn’t drop as much as many people think. Research shows that from the age of 30 it decreases by about 1-2% every ten years. So the drop is there, but not so big that we can blame a slow metabolism for the heavier weight loss. The fault here, too, is mostly in a poor lifestyle.[4,5,6]
Want to know more about when the metabolism slows down? In that case, we have an article for you At What Age Does Metabolism Slowdown Occur? Much Later Than One Might Expect.
2. Gender
Men typically have a higher BMR than women, due to a greater proportion of muscle and less body fat. Of course, this may not always be the case. For example, a muscular female athlete may have a higher BMR than a man who is not active and does not engage in sport.
3. Body composition
Higher basal metabolic rates are generally experienced by people who have a higher proportion of muscle mass. As already discussed, muscle is more energy intensive than adipose tissue. They burn more calories, even when they are at rest. To give you an idea, a kg of muscle burns about 13 calories per day, while a kg of fat only burns about 4-5 kcal. Therefore, a more muscular person burns more calories than one who has little muscle, even when they are not moving at that very moment. [7]
4. Physical activity
Although basal metabolic rate itself does not include energy burned during movement, regular physical activity also has an effect on it. Again, this is muscle related. Active muscles burn more energy, so people who play sports have a higher energy expenditure than those who move very little. [2]
5. Hormones
Many of the hormones that keep the body running smoothly also have an effect on how much energy you burn. For example, the stress hormone cortisol affects the metabolic rate. When it is elevated for a long time, it can be reflected in a slower metabolism. Conversely, when catecholamines (adrenaline and noradrenaline) are elevated, basal metabolism speeds up. The body releases more of these hormones during acute stress or exercise.
The thyroid hormone thyroxine also plays havoc with BMR. Its low levels, typical of hypothyroidism (reduced thyroid activity), slows down basal metabolism. Conversely, hyperthyroidism speeds it up.
6. Health status
Do you believe that when you are sick you should eat less because, for example, you don’t move as much? That’s pretty far from the truth. Illnesses, whether various infections, inflammatory diseases or injuries can, on the contrary, increase your need for energy. The body needs it to regenerate and fight illness. Of course, not every health problem will significantly increase the need for calories, but in general, when you are sick, you certainly shouldn’t restrict yourself from eating.
Can you increase your basal metabolic rate?
From what we have just discussed, it is clear that you can also partially increase your basal metabolism itself. First of all, it will be more efficient when you have more muscle. Remember, the more muscular you are, the higher your basal metabolic rate. However, how many calories you burn at rest will also be affected by how often and intensely you move and what sports you participate in. The body burns more energy for some time after exercise, especially after strength training. Muscles need it to recover. By exercising, you can actually speed up your metabolism for a while.
However, don’t rely on the fact that three strength training sessions a week will speed up your basal metabolic rate and you’ll be fine. When you want to increase your daily energy expenditure, it’s all about how many calories you burn throughout the day. That’s why it’s extremely important to get moving outside of the one hour you spend on workouts.[2]
Do you need to know your basal metabolic rate if you want to lose weight?
As already discussed, knowing your BMR is a fundamental building block in planning your optimal energy intake, even when calculating your caloric deficit. Once you know your BMR, you can add to it the energy burned by digestion, movement, and reduce the resulting value by 10-20% to figure out how many calories to take in per day for weight loss.
- For a detailed method to calculate energy intake, check out our article How to Calculate Energy and Macronutrient Intake for Weight Loss or Muscle Gain?
- Our online calculator will also help you quickly calculate the recommended amount of protein, carbohydrates and fats.
What should you remember?
Basal metabolic rate is the basic amount of energy your body needs to function properly. To some extent it is determined by gender, hormones and health status, but you yourself can influence it mainly through body composition and movement. However, don’t confuse it with total energy expenditure. In addition to the basal metabolic rate, it also includes the energy burned during digestion and, more importantly, during movement. And why do you need to know this? If you want to calculate your optimal caloric intake, start by calculating your basal metabolic rate. Choose the correct formula and you’re good to go.
Have we made it clear to you what basal metabolism is? If the article was of value to you, please don’t keep it to yourself and share it with your friends and family.
[1] BURKE, L. Clinical Sports Nutrition. .
[2] DUYFF, R.L. Complete Food & Nutrition Guide. . New York: Academy of Nutrition and Dietetics, 2017. ISBN 978-0-544-52058-5.
[3] FRANKENFIELD, D. et al. Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults: A Systematic Review. I – https://www.jandonline.org/article/S0002-8223(05)00149-5/abstract?utm_source=chatgpt.com
[4] JOHNSTONE, A.M. et al. Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine. – https://pubmed.ncbi.nlm.nih.gov/16280423/
[5] PAVLIDOU, E. et al. Revised Harris–Benedict Equation: New Human Resting Metabolic Rate Equation. – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9967803/
[6] SABOUNCHI, N.S. et al. Best Fitting Prediction Equations for Basal Metabolic Rate: Informing Obesity Interventions in Diverse Populations. – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4278349/
[7] WANG, Z. et al. Resting Energy Expenditure: Systematic Organization and Critique of Prediction Methods. – https://onlinelibrary.wiley.com/doi/abs/10.1038/oby.2001.42
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