The BMR Calculator calculates your metabolic baseline rate (the lowest amount of energy expended while at rest in a neutral environment and in a post-absorptive state, essentially meaning the body has not eaten in 12 hours).
The BMR calculator is the minimal amount of energy exhausted while resting in a neutral environment and when the digestive system is inactive. Imagine a parked car: gas is being consumed even though it isn’t moving.
Just like the car, there are only a few functions that require energy, such as the heart, brain, kidneys, nervous system, intestines, liver, lungs, sex organs, muscles, and skin. More than 70% of energy (the calories consumed) during the day is due to staying alive while resting. In an average day, ~20% comes from physical activity, and 10% is used for thermogenesis (the metabolism of food).
The BMR calculator is measured in very specific conditions when the subject is fully awake. The person must be inactive or resting for sympathetic nervous system activity to be idle so that the measurement can be as precise as possible.
Usually, basal metabolism constitutes a person’s largest caloric need. The daily caloric need is the BMR value multiplied by a factor of an integer from 1.2 to 1.9 relative to their activity level and calculated through the BMR Calculator.
Often, BMR calculations are based on estimates from statistical data. The Harris-Benedict Equation was one of the first equations proposed; it underwent a revision in 1984 to improve its accuracy, remaining in use until 1990 when it was replaced by the Mifflin-St. Jeor Equation. The Mifflin-St Jeor has been found to be more accurate than the revised Harris-Benedict.
The Katch-McArdle Formula differs in this respect in that it measures resting daily energy expenditure (RDEE), which considers the subject’s lean body mass, unlike the Mifflin-St. Jeor or the Harris-Benedict. Of these equations, the Mifflin-St. Jeor is considered the most accurate for determining BMR calculator until the Katch-McArdle is applied to the leaner individuals who happen to know their body fat percentage. You may choose which equation is to be used in the calculation by opening the settings.
Below are three equations used by the calculator:
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
BMR calculator Variables Muscle Mass – Running and biking, for instance, are examples of aerobic exercises that, in this case, have no effect on the BMR calculator. However, activities such as anaerobic or weight-lifting do indirectly lead to a higher BMR since they build muscle mass, therefore increasing rest energy consumption.
The individual who has a greater muscle mass in his/her physical composition will thus require a higher BMR to sustain their body at a certain level and calculate the BMR through a BMR calculator.
Age – An individual who is older and more frail is therefore expected to have a relatively low BMR or in simple terms, the minimum caloric intake required to sustain the functioning of the organs at a certain level is fairly low.
Genetics – The BMR calculator is also impacted by a set of features inherited from family and then passed down from relatives.
Weather—Energy expenditure to synthesize a body temperature in a cold environment will raise BMR. Too much heat externally can also raise BMR when too much energy is needed internally to cool off the organs. An increase in BMR calculator is roughly 7% for every increase in internal body temperature by 1.36 degrees Fahrenheit.
Diet—Small bites eaten more frequently will increase BMR. Extreme dieting or starvation can decrease BMR by up to 30%. The human body makes a series of trade-offs, such as energy expenditure, alerts, self-maintenance, and cognition, to be able to efficiently operate under the severely limited energy it is designed to waste to sustain life.
Pregnancy – Internally ensuring the safety of a developing fetus will increase BMR, which is why pregnant women consume food more than normal. Menopause may also affect BMR, either raising or lowering it depending on the changes in the levels of hormones.
Supplements—Many supplements and medications increase BMR, especially for the purposes of weight loss. A common one is caffeine.
BMR Tests
The most accurate approach to determine an individual’s BMR is resting BMR measurement (calorimetry) or consultation with a licensed professional or specialist rather than relying solely on an online BMR calculator resource that utilizes unyielding calculations. These portable devices can be found in numerous health and fitness clubs, doctor offices, and even in weight loss clinics.
Resting Metabolic Rate
There is one important difference in meaning between the two terms: Resting metabolic rate, often abbreviated as RMR, refers to the speed at which energy is consumed by the body at rest but not in a completely inactive state. Also, it is sometimes referred to as resting energy expenditure, also known as REE. In simple terms, BMR represents the fully resting value of energy expenditure, while RMR defines the expenditure within a wide range above resting.
Modern Wisdom
As reported in a meta-analysis study of BMR* in 2005, it was shown that even when controlling for all factors of metabolic rate, isolation alone presents a mystery of 26% variability amongst individuals. In a nutshell, an average acknowledgement could lead one to believe that an average individual with an average diet will logically have BMR values lined up to expected ranges; there are some other baseline set factors that are still a mystery in determining BMR exactly.
Even in the most advanced cases, where specialists are employed, all BMR calculations have margins of error, and no method will be perfectly accurate. The BMR estimates forged are parts of a greater system that is still not completely understood and total daily energy expenditure (TDEE) is one of them.
BMR can provide the building blocks when pursuing a particular health or fitness goal, but not much else after that. Unsatisfactory outcomes can stem from an assumed BMR and therefore TDEE based on broad estimating, but tracking exercise, food intake, and other relevant factors on a daily basis through a journal can assist with identifying what works and what needs improvement.
The journal’s progress tracking combined with adaptation over time to what the person’s needs are works best for the individual’s achievement of goals.
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