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All You Need To Know About Resting Metabolic Rate (RMR)

Resting Metabolic Rate (RMR) is the number of calories (kcal) burned at rest to sustain life. Pretty important then I guess? That's why we are now measuring it!!

Every major bodily function involves the metabolism, from breathing to brain function. Variables such as age, sex, muscle mass and activity levels all affect your RMR. RMR is responsible for up to 70% of your total energy expenditure. Your brain alone uses roughly 300kcal a day?!

Two other things make up the remaining 30% of your total energy expenditure. First, the Thermal effect of food (10%), that is, the energy required during digestion to break down more energy for you to utilise. Second, activity energy expenditure (20%), which as the name suggests regards your daily movement. We usually put these into two subcategories for clarity, either exercise activity or non-exercise activity such as walking to work.

INDIRECT CALORIMETRY (breath analysis) is considered the absolute gold standard for measuring RMR, often used in clinical or research settings. By measuring oxygen consumption (VO2) and carbon dioxide production (VCO2), we can ascertain something called a respiratory exchange ratio (RER). Simply put, this tells us what fuels are being utilised (either carbohydrates or fats) and the distribution of these fuels at rest over a period of 10 minutes. This can then tell us exactly how many kcal you use to sustain the above bodily functions.

To some, you may be already familiar with the term RMR as It is commonly prompted by diet and exercise apps asking you to input things like age, sex, height and weight. This will then give you a predicative RMR and proposed daily kcal value based on your goals e.g. weight loss. But this equation which tries to estimate RMR can be inaccurate BY UP TO 40%. So, if your goal is to lose weight, you may have an error of up to 40%, leading to either massive over or under estimation of kcal intake. Indirect calorimetry completely removes this guesswork and gives you exactly the information you need.

It is not all just about accurate kcal measurements. RMR also gives great insight into metabolic health, highlighting the distribution of fuels being utilised at rest. We know using more carbs at rest can be considered as inefficient, and a strong indicator of poor cellular health and aerobic fitness. A normal distribution of these fuels at rest should be 70% fat and 30% carbs. Why is this important? Well, a poor capacity for fat utilisation at rest is clearly implicated in the manifestation of chronic metabolic diseases and is associated with weight gain and co-morbidities. Largely, it is the hallmark of ‘metabolic inflexibility’ and precursor for type 2 diabetes. It is also a marker of poor aerobic fitness largely due to the inefficiency and reduced number of mitochondria, nicknamed the energy powerhouse of the cel). Luckily for us, we can improve mitochondria function and therefore metabolic health by appropriate training!!!

So what does the test involve?!

The test involves lying down in a rested state (4 hours fasted) breathing as normal for 10 minutes with a mask on around your nose and mouth attached to our PNOE device. After 10 minutes is up, we will be able to discuss initial feedback from the device, with a full individualised report sent to you within 24hrs! Look below to see what some of a test report looks like!

Fig. 1. RMR and recommended kcal intake for training goals

Fig. 2. Fat vs CHO utilisation at rest

With all this powerful knowledge we can then help prescribe the most appropriate training plan for your fitness goals and health. This test is for absolutely anyone who is interested in getting accurate objective data regarding their kcal intake and metabolism. Whether your goal is to lose weight, put on muscle, improve aerobic fitness or have a better understanding of how your metabolism works, then it is an absolute must!

When can you book?!

From Monday 4th of April we are launching this service! Please get in contact for further information!


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