What is basal metabolic rate (BMR)?

Your basal metabolic rate (BMR) is the number of calories your body burns daily without your having to do anything. Your body uses around 75 percent of the calories you eat each day just to maintain life and perform basic functions. You expend energy just to breathe, build new red and white blood cells, tone your muscles, pump blood throughout the body, think, raise or lower your body temperature -- even while you're sleeping. Any activity you do in addition to these natural functions also requires fuel in the form of calories. If you eat more calories than your body metabolism needs daily, you will gain weight. There are 3,500 calories in every pound of body fat. That means that if you eat 500 calories more per day than your body needs, you will gain one pound every week.

Basal metabolic rate (BMR) is the average daily amount of energy (calories) that is used by a body when it is at rest. Heredity, height, body composition, and age determine a person's basal metabolic rate. It is also known as basal energy expenditure (BEE).

The energy in a person's BMR is used to keep body temperature normal and to power the heartbeat, breathing, and other organ functions. Your BMR uses up about two-thirds of your daily calories.

The best measure of BMR is taken when you are not digesting any food or doing any activity, usually right after waking up for the day.

Another option is to measure resting metabolic rate (RMR), also known as resting energy expenditure (REE). This is very similar to BMR, but the test can be done with fewer restrictions.

Basal metabolic rate (BMR), also called the resting metabolic rate, is the amount of energy needed to support the body's most basic functions when at rest in a neutral, or non-stressful, environment. The BMR is the number of calories a specific human needs per day to stay alive. BMR can be responsible for 70% of the calories burned per day.

The body's most basic functions are those that are immediately necessary for a person to stay alive. These functions include pumping blood, breathing and producing heat. Nonessential functions, such as digestion and standing are not included in this calculation.

The BMR was originally created as a tool for measuring the thyroid status of humans by comparing the metabolic rate of animals to that of humans. Today, the BMR is used as a measure of an individual's metabolism, which changes with age, weight, height, and a variety of medical conditions. A person's exercise habits may affect their BMR.

Both basal metabolic rate and resting metabolic rate are usually expressed in terms of daily rates of energy expenditure. The early work of the scientists J. Arthur Harris and Francis G. Benedict showed that average values could be derived using body surface area (calculated from height and weight), age, and gender along with the oxygen and carbon dioxide measures taken from calorimetry. Studies also showed that by eliminating the gender differences that occur with the accumulation of adipose tissue by expressing metabolic rate per unit of "fat-free" or lean body weight, the values between genders for basal metabolism are essentially the same. Today there are less time intensive tests that are often used in place of the BMR test.

BMR calculations are increasingly being used by the public to formulate weight loss plans that proponents claim can be tailored to the needs of the individual.

Today, the BMR is under preliminary investigation to estimate everything from reproductive success to diabetes risk. The results of such inquires remain unknown.

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