The basal metabolic rate (BMR) is the amount of energy needed while resting in a temperate environment when the digestive system is inactive. It is the equivalent of figuring out how much gas an idle car consumes while parked. In such a state, energy will be used only to maintain vital organs, which include the heart, lungs, kidneys, nervous system, intestines, liver, lungs, sex organs, muscles, and skin. For most people, upwards of 70% of the total energy (calories) burned each day is due to maintenance. Physical activity makes up about 20% of expenditure, and about 10% is used for the digestion of food, also known as thermogenesis.
What is a healthy BMR?
This will be different for each person. Since most of your basal metabolic rate comes from things you can’t control, like breathing and pumping blood, day-to-day changes don’t have much effect on this number. But building more muscle does raise BMR because muscle is “hungry” for energy and it takes more energy to keep more muscle. This means that if you have a lot of muscle, you’ll burn more calories even when you’re not doing anything.
Your “total daily energy expenditure” (TDEE) is the number of calories your body uses in a day as a whole. It’s based on your basal metabolic rate (BMR) and how active you are during the day. This depends a lot on how active you are, how old you are, and what gender you are. To get a more accurate answer, you can use a TDEE calculator or calorie calculator to find this number. Keep in mind, though, that you can’t know your exact TDEE because your activity level changes every day, and the only way to get 100% accurate BMR numbers is to get tested in a lab.
What’s the difference between BMR and RMR?
The term “BMR” is sometimes used in the same way as “RMR,” which stands for “resting metabolic rate.” The difference is that BMR only looks at how much energy it takes to breathe, circulate blood, and keep your body temperature stable when you are completely still, while RMR also looks at how much energy it takes to digest food and do daily tasks like getting dressed and lifting your fork to your mouth.
BMR and RMR numbers are usually close enough that they can be used interchangeably. However, if you are trying to gain or lose weight, you should pay attention to which number an equation calls for. If it’s based on BMR, you can use the calculator above to get a rough estimate. If the equation needs RMR, use our RMR calculator, which will give you a slightly higher number.
How can I use my BMR to lose fat or gain muscle?
When you use your BMR to figure out your TDEE, you can make sure that your nutrition plan fits your level of energy use and doesn’t give you too many or too few calories. Having this information instead of guessing or blindly following a plan that doesn’t fit your needs can make or break your ability to gain muscle or lose fat.
The BMR is measured under very restrictive circumstances while awake. An accurate BMR measurement requires that a person’s sympathetic nervous system be inactive, which means the person must be completely rested. Basal metabolism is usually the largest component of a person’s total caloric needs. The daily caloric need is the BMR value multiplied by a factor with a value between 1.2 and 1.9, depending on activity level.
In most situations, the BMR is estimated with equations summarized from statistical data. The Harris-Benedict Equation was one of the earliest equations introduced. It was revised in 1984 to be more accurate and was used up until 1990, when the Mifflin-St. Jeor Equation was introduced. The Mifflin-St. Jeor equation has been shown to be more accurate than the revised Harris-Benedict equation. The Katch-McArdle Formula is slightly different in that it calculates resting daily energy expenditure (RDEE), which takes lean body mass into account, something that neither the Mifflin-St. Jeor nor the Harris-Benedict Equation does.
Of these equations, the Mifflin-St. Jeor Equation is considered the most accurate equation for calculating BMR, with the exception that the Katch-McArdle Formula can be more accurate for people who are leaner and know their body fat percentage. You can pick the equation to be used in the calculation by expanding the settings.
BMR Variables
Muscle Mass: – BMR is not affected by aerobic exercises like running or cycling. But anaerobic exercises, like weightlifting, indirectly raise the BMR because they build muscle mass, which makes the body use more energy at rest. The more muscle mass a person has, the higher their basal metabolic rate (BMR) needs to be to keep their body at a certain level.
Age: – The BMR of a person is lower if they are older and more flexible. This means that they need fewer calories to keep their organs working at a certain level.
Genetics: – Hereditary traits passed down from ancestors influence BMR.
Weather: – Cold places raise BMR because it takes more energy to keep the body’s temperature stable. In the same way, too much heat from the outside can raise BMR because the body has to use energy to cool down the organs inside. When the body’s internal temperature goes up by 1.36 degrees Fahrenheit, BMR goes up by about 7%.
Diet: – BMR goes up when you eat small meals often. On the other hand, being hungry can lower BMR by up to 30%. Like a phone that goes into power-saving mode when it has 5% of its battery left, a human body will sacrifice things like energy levels, moods, keeping its body in good shape, and brain functions to make the most of the few calories it needs to stay alive.
Pregnancy: – Taking care of a separate fetus inside the body raises BMR. Because of this, women who are pregnant tend to eat more than usual. Changes in hormones during menopause can also raise or lower BMR.
Supplements: – Some supplements or drugs raise BMR, most of the time to help people lose weight. Most people use caffeine.
BMR Tests
Online BMR tests that use strict formulas are not the best way to figure out a person’s BMR. It is better to talk to a trained specialist or use a calorimetry device to measure BMR. Many health and fitness clubs, doctor’s offices, and weight-loss clinics have these hand-held devices for sale.
Resting Metabolic Rate
Even though they are both used in the same way, there is a big difference between what they mean. Resting metabolic rate, or RMR for short, is the rate at which the body burns energy when it is relaxed but not completely inactive. It can also be called REE, which stands for “resting energy expenditure.” When measuring BMR, the body must be in total physiological equilibrium, but when measuring RMR, the conditions can be changed and are based on the situation.
Modern Wisdom
A meta-analysis study on BMR* done in 2005 showed that even when all the factors that affect metabolic rate were taken into account, there was still a 26% difference between people. Basically, a normal person who eats a normal diet will likely have BMR values that are expected, but there are still some things about BMR that are not fully understood.
So, even when experts use the most accurate methods to calculate BMR, the measurements won’t be perfect. We don’t fully understand all of the ways the human body works yet, so estimating the total daily energy expenditure (TDEE) from the BMR is just that: an estimate.
BMR can help you get started on your way to any health or fitness goal, but it doesn’t have much else to offer after that. Calculating your BMR and, by extension, your TDEE may not give you the results you want because they are only rough estimates. However, keeping a daily journal of your exercise, food intake, etc., can help you keep track of the factors that lead to any given result and figure out what works and what needs to be changed. Most of the time, the best way to see how close you are to reaching personal goals is to keep a journal and make changes as needed over time.
The three equations used by the calculator are listed below:
Mifflin-St. Jeor Equation:
For men:
BMR = 10W + 6.25H + 5A + 5
For women:
BMR = 10W + 6.25H – 5A – 161
Revised Harris-Benedict Equation:
For men:
BMR = 13.397W + 4.799H – 5.677A + 88.362
For women:
BMR = 9.247W + 3.098H – 4.330A + 447.593
Katch-McArdle Formula:
BMR = 370 + 21.6 (1 – F)W
where:
W is body weight in kg.
H is body height in cm; A is age.
F is body fat in percentage.