What is your Metabolism or Metabolic Rate?

Your metabolism refers to a range of biological processes taking place within your body’s cells and how many calories it takes to do that work. This can also be written as your total daily energy expenditure. Your Metabolism is made up of 3 variables

  1. Resting Metabolic Rate
  2. Structured physical activity/exercise 
  3. Activities of daily living including thermic effect of food

What is Resting Metabolic Rate (RMR)?

The energy required to sustain your life at rest i.e. the amount of energy required to keep you living (blood pumping, brain working, lungs breathing). This accounts for roughly 60-65% of your total daily energy expenditure.

Why Measure RMR?

Given your RMR accounts for 60-65% of your body’s total daily energy expenditure, once you know this amount, you can determine your appropriate calorie intake and macronutrient split in order to either lose fat mass or increase lean mass. It becomes a simple maths equation, eat less than your body burns to be in a calorie deficit, eat more than your body needs to be in a calorie surplus. The important part is knowing how much less or how much is required without impacting resting metabolism. We have two appointment types for RMR testing. One is the RMR test, results/report and explanation and the other appointment also includes a DEXA scan and long consult. 6

How is RMR measured? 

RMR is measured through Indirect calorimetry which measures the composition of your breath determining your gas flows, volumes and concentrations of O2 and CO2. By determining how much oxygen you use and how much carbon dioxide you expire, we can accurately measure the rate at which you consume energy at rest, your resting metabolic rate (RMR).

What does the test involve?

It is actually a very relaxing test! You will be required to lay quietly in a reclined position for 10 minutes while wearing a special mask connected to a gas analyser, and a heart rate monitor. No special clothing is required but it may be helpful to wear something comfortable to help stay relaxed during the test.  Data from the test is then downloaded for analysis and a report produced.

In order for the test results to be as accurate as possible it is very important that the following the pre-test guidelines are followed.

RMR pre-test guidelines;

  • At least 5 hours of fasting prior to the test (no/limited water intake either ideally)
  • No intense exercise (greater than 1 hour) 24 hours before the test
  • No caffeine, tobacco or stimulating drinks for at least 5 hours prior to the test
  • Continue medications as usual — be prepared to discuss before your test begins


What Is considered Structured physical activity/exercise?

The energy you use by being active. This comprises about 15 to 30% of the total amount of energy you burn through every day—and it includes gym sessions, walking the dog & generally any planned cardio exercise. 

What are Activities of daily living & the thermic effect of food?

A term for the number of calories you burn by doing everything else in your life including washing dishes, even fidgeting. This also includes chewing and digesting what you eat and absorbing and storing those nutrients. It accounts for about 10% of your total daily energy expenditure.

Ok so I have my RMR, what do I do with it?

A measure of energy expenditure at rest or RMR gives you the ability to personalise food requirements your body requires to optimise your health goals whether that be for fat loss or increasing lean mass. Once you know your RMR you have a cheat sheet for your body and can start to manipulate your food intake to help reach your goals more effectively and efficiently. We recommend you also track your changes with a DEXA scan which will demonstrate how your fat mass and lean mass (body composition) is changing due to your new regime.

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