The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


Resting Metabolic Rate – What is it, and Why is it Important?

Posted in

Monday, Nov 01, 2021

Metabolic rate has long been a buzzword in the health and fitness industry, particularly among individuals who are trying to achieve or maintain a healthy body weight.

Resting metabolic rate (RMR) is defined as the rate at which an individual burns calories while at rest. A calorie is a unit of heat. Therefore, RMR can also be viewed as the body’s rate of heat production while at rest. Since there are several factors that affect RMR, this value varies among individuals. 

Over the course of a day, there are three factors that determine total caloric expenditure. Believe it or not, for most people RMR accounts for approximately 60-70% of the total daily caloric expenditure! Physical activity typically accounts for anywhere between 10-30% of total daily caloric expenditure, depending on how active (or not) you are. The remaining 10% of daily caloric expenditure comes from the “work” of the process of digestion. From this information, it should be easy to see that having a relatively high resting metabolic rate is desirable for the purposes of weight control.

Because there is a very strong correlation between the amount of oxygen your body is using (oxygen consumption) and metabolic rate (caloric expenditure), it is possible to measure RMR quite accurately. Many colleges, universities, and hospitals have the capability to measure RMR in their Human Performance Laboratories. Since eating and physical activity tend to increase metabolic rate, standard procedures for measuring RMR include performing the measurement first thing in the morning following a 12-hour fast. After lying quietly for approximately 10-15 minutes in a dimly lit room, a nose clip and breathing apparatus are attached to the individual. Exhaled air is collected and analyzed for oxygen content. By comparing the amount of oxygen present in the inhaled air versus the amount of oxygen in the exhaled air, the amount of oxygen used by the body is calculated. Recall that there is a very strong correlation between oxygen consumption and caloric expenditure. Once we know the former, the latter is easily calculated. It may surprise you to learn that this procedure has been utilized extensively in thousands of labs worldwide since the 1920s!

RMR can also be estimated through the use of formulas.

While this method is not quite as accurate as an actual measurement, it is much more convenient. The most commonly used equation to estimate RMR is the Mifflin-St. Jeor Formula. The formulas (one for men and one for women) provide a good estimate of resting daily caloric expenditure, which again, is the same thing as resting metabolic rate.

RMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) + 5

RMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years)  – 161

Note: to determine your weight in kg, divide your weight in pounds by 2.2. To determine your height in cm, multiply your height in inches by 2.54. To save time, simply use your browser to find the Mifflin-St. Jeor Formula and enter your numbers.

There are many factors that affect resting metabolic rate. Among them are age, gender, body weight and body composition (the ratio between lean versus fat tissue), and genetics. Several hormones such as the thyroid hormones (T-3 and T-4), testosterone, epinephrine and norepinephrine, as well as growth hormone also have a significant effect on resting metabolic rate. While the exact numbers remain somewhat elusive, it has long been known that when compared pound for pound, muscle tissue burns more calories per minute at rest than fat tissue. Logic tells us that one way to increase resting metabolic rate is to increase muscle mass.

The most effective way to accomplish this goal is by performing moderate intensity strength training on a regular basis (at least 2-3 days per week) in addition to regular aerobic activity. At the same time, the individual must be in positive caloric balance (consuming more calories than expending). While protein needs are increased somewhat for lean mass gains, large amounts of dietary protein and protein supplements are not required to accomplish this goal. The upper limit of protein intake for individuals who are striving to increase muscle mass is approximately 0.75 grams of protein per pound of body weight per day.

As an example, a 160 lb individual would need no more than about 120 grams of protein per day in order to increase muscle mass. This requirement can be easily met by selecting a wide variety of heart-healthy protein sources daily. Examples are beans, green vegetables, whole grains, nuts and seeds, reduced-fat dairy, fish, poultry, and soy.

To summarize, resting metabolic rate (RMR) is simply the number of calories burned by the body per minute while at rest, and is synonymous with heat production by the body at rest.

RMR can be measured in a clinical setting or estimated by using the Mifflin-St. Jeor Formula. A great way to increase your RMR is to increase your level of physical activity. Be sure this includes at least 2-3 days per week of moderate intensity strength training.