Predicting Resting Metabolic Rate (RMR)

One of the most common questions we get asked here at MeasureUp is how our estimate of your resting metabolic rate (RMR) compares with an “actual” measure of RMR.

When I first started in the DEXA game in 2006 there was a paper released that I used to base my decision to estimate RMR rather than “measure” RMR. The aim of the paper published in the European Journal of Clinical Nutrition (2007) 61, 582–589 was to investigate whether the prediction equations from different body composition measurement techniques were accurate. The study used the gold standard indirect calorimetry and the RMR estimate equations were predicted from fat fee mass. The results suggested that choosing the appropriate RMR predictive equation should be based on the people you are scanning (especially in a business such as MeasureUp). The other interesting point shown was the less precise measurement of fat free mass (SF and BIA) was also shown to adversely affect the accuracy of RMR prediction.

Clinics are now popping up providing RMR measurement using indirect calorimetry? It’s important to remind you of what’s required for a gold standard RMR measurement. In my other life as a senior research fellow in the obesity and exercise domain I conducted over 1000 RMR investigations using indirect calorimetry. Standard protocol for such a test is as follows:

– No exercise 24 hours prior to the test

– Overnight fasting required

– You must be rested (lying down) for at least 30 minutes prior to the measurement

– A minimum of 10 minutes of gas collection is required

Unfortunately, the increase in RMR testing may lend itself to a bending of these critical standards of testing and ‘cutting corners’ so to speak. If you are going to have an RMR test and have it measured using indirect calorimetry do not break the rules above as it will alter the test result significantly and you are spending top dollar for these tests. Also, ask the following questions about the device they use:

• All devices must measure O2 and CO2 independently by separate sensors

• These two sensors must be calibrated daily with a known gas (O2 and CO2)

• If the device is only measuring O2 and a prediction for CO2 is used – don’t use this tool.

Finally, the work that we undertook with our tests we found that prediction using Cunningham’s Equation vs indirectly calorimetry was 20-80 calories out. This will not impact on your ability to lose fat. That’s the next story…

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