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What is BMR and how can it help you?

Terms related to metabolism are gaining more attention in health care settings and amongst fitness enthusiasts trying to lose weight by “boosting” their metabolism or eating below their caloric needs. You may have heard terms like basal metabolic rate (BMR), total daily energy expenditure (TDEE), and resting metabolic rate (RMR). 

Can knowing your daily calorie needs by calculating your basal metabolism—the energy required to maintain basic life-sustaining functions while at rest—make a difference to your current weight?

Let’s dive in and find out about one of these metrics, BMR, how it differs from a similar one, RMR, and whether calculating calorie requirements and the amount of calories you burn each day can help you realistically achieve your fitness goals.

What does BMR measure?

When you wake up in the morning, before you get up, drink coffee, or even go to the bathroom, your physical activity level is as low as it gets, and your body needs the least number of calories to function. The necessary energy is just enough to “keep the car running.” The rate at which your body burns calories in this state is called basal metabolic rate. It accounts for about 60%-70% of your total daily energy expenditure. Most people fall within a BMR range of 1000-2000 kcal per day. 

How BMR and body composition are related

The more lean body mass you have, the higher your calorie needs and BMR. Scientific studies show that building muscle has consistently shown improved glucose metabolism. 

A lower BMR, on the other hand, is linked to a higher body fat percentage. It probably isn’t surprising to learn that a lower BMR is also associated with an increased risk of insulin resistance and type 2 diabetes. 

Is a higher BMR always a good thing?

A higher BMR may sound like a good thing, since it’s often associated with a faster metabolism and greater muscle mass. Counterintuitively, though, having a higher BMR is not always indicative of better health. A high BMR can, in fact, be reflective of an underlying inflammatory condition, a thyroid condition, or immune issue.

What is a BMR formula?

The gold standard for measuring metabolic rate is still indirect calorimetry. This test analyzes the oxygen and carbon dioxide levels in a person's breath and uses the results to calculate the heat the body produces to determine the metabolic rate by measuring the pulmonary gas exchanges. 

For an easier, at-home measurement, a number of formulas estimate the basal metabolic rate of your body based on your height, current weight, and age. The Mifflin-St Jeor, the Katch-McArdle, and the Harris-Benedict are commonly used equations to estimate BMR. 

How accurate is a BMR calculator—and can I use one to lose weight?

Remember that a BMR calculator is still just an estimate. Several factors that aren’t considered by these calculations can affect the rate at which your body burns calories. If your body is too hot or cold because of your environment, your metabolism will work extra hard to maintain body temperature. You may also be taking supplements or medications that increase your metabolism. These other factors indicate that a BMR is just a general target and not a strict determinant of your daily calorie needs.

However, if you want a general idea,  use our tool below. It uses the Mifflin-St Jeor equation, introduced in 1990, which measures a similar though slightly different metric than the BMR called resting metabolic rate (RMR). RMR and BMR are often used interchangeably, though there is one key difference—RMR estimates your caloric needs under minimal, rather than zero, activity conditions. Think desk job rather than lying in bed. The  Mifflin-St Jeor equation is more accurate across a broader range of individual weights than the Harris-Benedict formula. After calculating RMR, the tool layers on activity level to estimate your total energy expenditure—and your estimated calories for the day. 

A recent review of equations for estimating BMR found about 248 different equations. There has obviously been a lot of effort put into coming up with more accurate calculations! The same review concluded that, while BMR calculators are great for determining general targets for a weight loss program, they aren’t as helpful for individuals, and, given their margin of error, they are best used as a general guideline.

Your body is unique—your approach to health should be too

We know that body weight is not determined by total calorie intake, the number of workouts you have per week, willpower, or even metabolism—it is a complex combination of factors that can include genetics, environment, health conditions, and lifestyle. Dietary and lifestyle changes don’t produce consistent effects for all individuals. 

At Found, our care providers specialize in obesity medicine and can personalize a weight care program that fits your lifestyle. The most effective approach to help you lose weight is the one that works with your biology. Our providers use a proprietary assessment called MetabolicPrint™ to help tailor care and prescribe medicine. You’ll also work with a certified personal health coach to help you stay focused on what’s most important for your journey and health.

Meet the author
TJ Carlin
Freelance Health Strategist & Copywriter
TJ Carlin enjoys collaborating with brands that apply the latest in science to products and services that put humans and their experiences first.
Medically reviewed by:
Katherine St. Jacques MS, RDN, CDCES
Fact checked by:
Lisa Greissinger
Edited by:
Shaun Chavis
Last updated on:

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