Resting Metabolic Rate (RMR)
What Is the Resting Metabolic Rate?
Definition
Metabolism is the process by which your body changes the food and liquid you take in into energy for use.
The Resting Metabolic Rate or RMR is the minimum number of calories you need to perform basic functions, such as maintaining heart rate and body heat, breathing and keeping up brain activity. You will need this minimum amount of energy each day, even if you are not moving around. Two people with the same weight and height can have very different metabolic rates and energy needs.
The RMR Test: How It Works
The Fitnescity RMR test uses state-of-the-art technology to measure the number of calories your body needs at rest, that is, the number of calories your body needs to perform basic functions. From that number, a specialist (an endocrinologist or a clinical dietitian) will use your results to determine how many calories you need in a day to lose, maintain, or gain weight. The test results you receive in your Fitnescity report include the RMR and your Total Energy Expenditure, or the number of calories you burn in a day.
© FITNESCITY - Sample RMR Report
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Some RMR machines also measure your Respiratory Exchange Ratio (RER), which indicates whether you burn more carbs or fat. Healthy individuals should be able to rely mostly on fat for energy.
The RER is the ratio between the amount of carbon dioxide (CO2) produced in metabolism and oxygen (O2) used. This ratio indicates what your body is using for energy: carbohydrates or fat. At rest, the RER is about 0.8. However, during exercise the number can exceed 1 as CO2 production by the working muscles becomes greater and more O2 is being used.
An RER of 0.70 means that your predominant energy source is fat while an RER of 0.85 suggests that you use a mix of fat and carbohydrates. If the value is 1.00 at rest, this means that your body relies mostly on carbohydrates for energy.
© FITNESCITY - Sample RMR Report
How to Use Your RMR Results
Once you have your RMR results, you can easily calculate your Total Energy Expenditure based on your activity level.
Here’s how you can do it:
Without an accurate test, you could use your weight, height and age to estimate your RMR. However, everyone is different, and a small difference in your RMR can have a significant impact on your diet over time.
Get an RMR test with Fitnescity
Your Measured RMR Will Most Likely Be Different than Your Estimated RMR
You can estimate your RMR using the Mifflin-ST Jeor equation. However, the formula does not take into account all of the factors mentioned above, and as a result, it can under-estimate or over-estimate the RMR.
Men : 10 x weight (kg) + 6.25 x height (cm) – 5 x age + 5
Women : 10 x weight (kg) + 6.25 x height (cm) – 5 x age – 161
It is important to keep in mind that the equation cannot entirely be relied upon, since each individual is different. For instance, you might find that your actual (measured) RMR is 200 calories less than your estimated one. The difference is enough to cause weight gain of several pounds over a few months.
© FITNESCITY - Sample RMR Report
Factors That Affect Your Metabolism
Age
The metabolic rate declines with age because of loss of skeletal mass in increased percentage of fat tissue.
Body Fat Percentage
Your RMR depends on the amount of fat you have. If your body fat percentage is high, your RMR might be lower than that of an individual with a lower body fat percentage.
Gender
The RMR is lower in women than in men, mostly because men, on average, have a greater muscle mass and a lower body-fat percentage than women.
Weight
A smaller body requires fewer calories to maintain the same physiological functions, whereas a larger body requires more calories.
Also, during weight loss your body may try to conserve energy in response to a lower calorie intake, this can also cause a reduction in RMR.
Height
Taller people typically have greater body surface area and more lean body mass. As a result, they can have a higher RMR.
Body temperature
For every increase of 0.5 degrees C in internal temperature of the body, the RMR increases by about 7 percent. Therefore, a person with a fever of 42 degrees C (about 4 degrees C above normal) would have an increase of about 50 percent in RMR.
Diet
Starvation or serious abrupt calorie-reduction can dramatically reduce the RMR by up to 30 percent. Likewise, restrictive, low-calorie weight-loss diets may cause the RMR to drop by as much as 20 percent.
Exercise
Physical exercise not only influences body weight by burning calories, it also helps raise RMR by building extra muscle. The greater the exercise intensity, the longer it takes the body to recover, which results in a longer and higher excess post-exercise oxygen consumption (EPOC).
External temperature
Temperature outside the body affects the resting metabolic rate. Exposure to cold temperature causes an increase in the RMR, as the body tries to create the extra heat needed to maintain its internal temperature. A short exposure to hot temperature has little effect on the body’s metabolism because of compensatory increases in heat loss. However, prolonged exposure to heat can raise the RMR.
Genetics
Some people are born with faster metabolisms, while others naturally have slower metabolisms.
Hormones
Some hormones can increase or decrease metabolic rate. For instance, the thyroid hormones regulate a portion of metabolism. An individual who has hypothyroidism can have a low RMR.
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How to Boost Your Metabolism
Eating enough protein will allow your body to build and repair its muscle tissue. As a result, this will help you maintain or develop your muscle mass.
Increasing your daily activity level, including through strength training, will not only burn more calories, but also strengthen your muscle mass.
Eating less sugar (and more protein and fat) will boost your RMR; the amount of energy that the body requires to process sugar is relatively small compared with that required to process fat and/or protein.