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Resting Metabolic Rate (RMR) Testing


 

What is Resting Metabolic Rate (RMR)?

Metabolism, quite simply, is the conversion of food to energy.

Metabolic rate is a measure of how much food, or fat, is converted to energy in a day. Resting metabolic rate (RMR) or Actual Resting Energy Expenditure (AREE) is the measurement of how much food, or energy, is required to maintain basic body functions such as heartbeat, breathing, and maintenance of body heat while you are in a state of rest. That energy is expressed in calories per day. So an RMR test shows how many calories you burn at rest, doing nothing more than sitting in a chair.

Metabolic Testing measures how many calories someone is burning and enables us to see if they are burning more or less than they should. When a person is underfed, it also measures how much lean mass (muscles, brain, organ tissue, etc.) is being used to fuel the body. In slightly more technical terms, metabolic testing measures an individual's metabolic rate by determining the Actual Resting Energy Expenditure (AREE), namely, the amount of calories burned while in resting state. It does this by measuring oxygen and carbon dioxide exchange, a process called indirect calorimetry. 

During the testing procedure, an individual reclines and breathes under a lightweight canopy hood for 20-30 minutes. Immediately after the procedure, the nutritionists analyzes the RMR/AREE alongside the PREE (predicted resting energy expenditure) to assess if the body is burning the number of calories it should (a normal metabolism), fewer calories than it should (hypometabolic) or more calories than it should (hypermetabolic). 

HOW DOES IT WORK?

Indirect calorimetry (a measurement of metabolic rate) relies on the fact that burning 1 calorie (Kilocalorie) requires 208.06 milliliters of oxygen. Because of this very direct relationship between caloric burn and oxygen consumed, measurements of oxygen uptake (VO2) and caloric burn rate are virtually interchangeable.

Oxygen uptake requires a precise measurement of the volume of expired air and of the concentrations of oxygen in the inspired and expired air. The process requires that all of the air a person breathes out be collected and analyzed while they rest quietly. The indirect calorimeters contain a precision air flow sensor that measures the volume of expired air, and an oxygen sensor that measures the concentration of oxygen. Once the factors of humidity, temperature and relative humidity are accounted for, the instrument provides the most accurate results available in a compact metabolic analyzer.

HOW IS A TEST PERFORMED?


Pre-test Requirements

It is desirable to measure a person’s metabolic rate at a true resting level. To ensure one is at rest, we recommend the following preparation:

  1. Avoid eating a meal 4 hours before the test.
  2. Avoid exercising on the day of testing.
  3. If possible, avoid the use of stimulants such as caffeine prior to testing.
  4. During the test it will be important to get into a comfortable position and relax as much as possible.
  5. Keep lips sealed lightly around the mouthpiece. It is important that all the air breathed out is analyzed by the MetaCheck™.

Testing

  1. The patient will place a nose clip on his nose and the mouthpiece in his mouth, using his lips to seal around the edges. The patient should be relaxed and breathe normally.
  2. After approximately 10 minutes, the machine will end the test and prompt the tester to enter in patient data to compare patient results to averages. The machine analyzes the AREE alongside the PREE (predicted resting energy expenditure) to assess if the body is burning the number of calories it should (a normal metabolism), fewer calories than it should ( hypometabolic), or more calories than it should (hypermetabolic). The results can then be printed out.

WHY TEST RMR?


Why Test RMR to Treat Obesity

Proof of “normal” metabolism

Most overweight people are convinced they have a slow metabolism. The truth is that statistically, most overweight and obese individuals have average or higher than average metabolic rates. Taking a measurement removes this excuse. Seeing that their bodies can indeed burn calories can be very encouraging and motivating.

Stabilize weight loss

Regardless of the method used to lose weight, a patient’s RMR will decrease after weight loss. The decrease is actually below the level predicted by fat-free mass (FFM). Although the cause is unclear, it appears that in most cases, if a patient can maintain his new weight for 6 months, his RMR will eventually rise to the expected level. Pinpointing the precise number of calories necessary to maintain is key to surviving this crucial period.

Pinpoint caloric weight loss zone

When restricting calories, knowing a baseline RMR is invaluable. Metabolic testing can calculate a “weight loss zone” for 1 ½ pound per week weight loss, or practitioners can use the RMR to calculate a caloric goal unique for their patients.

Detection and Diagnosis of hypo-metabolism

In cases where a patient has a clinically low metabolic rate, further diagnosis and treatment by a physician will be required before successful weight loss can be achieved.

Assess the effect of weight loss treatment on metabolism

Once calories are restricted, medications are introduced, or an exercise plan has been implemented, the human body will respond. This is especially true of significant interventions, such as bariatric surgery. The caloric goals of a dietary plan will rarely sustain a patient throughout an entire weight loss regimen. The result is the dreaded “plateau.” Periodic assessment of RMR will show the effects of the treatments and allow adjustments to the caloric goals.

Why Test RMR for Nutritional Assessment

  • Proper nutritional care is VITAL for the hospitalized patient. Studies show that hospital stays are reduced an average of 60% when nutritional status is evaluated and needs are met.
  • The formulas that predict caloric needs for nutritional assessment (Harris Benedict, Miffin, etc) are inadequate for certain populations, especially sick or hospitalized patients. RMR is recommended for the following populations:All patients receiving parental or enteral nutrition
    • Hypermetabolic patients (burns, trauma, sepsis, head injury)
    • Starvation-adapted or malnourished patients
    • Extremely obese patients (>=200% of ideal body weight)
    • Patients with non-healing wounds
    • Patients with abnormal body composition (multiple sclerosis, cerebral palsy, cystic fibrosis, spinal cord injury, amputations).
    • Patients who can benefit from education about appropriate calorie intake.

The Print Out

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230 N Maryland Avenue, Suite 110
Glendale, CA 91206
Phone: 818-275-2769
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