WHAT IT IS
What is resting metabolic rate testing?
Resting metabolic rate (RMR) is the energy your body uses at rest for essential functions, breathing, circulation, cellular repair, and it typically accounts for 60 to 75% of daily energy expenditure. The test is simple and non-invasive: you breathe into a device that measures oxygen consumption and carbon dioxide production, allowing us to calculate your true energy expenditure and your fuel mix.
WHAT IT REVEALS
Why it matters
True daily energy expenditure, so nutrition is neither over- nor under-fuelled
Metabolic adaptation, identifying when repeated dieting has lowered output
Fuel utilisation, whether you primarily burn carbohydrate or fat
Most people rely on calculators that can be inaccurate by hundreds of calories, the difference between losing fat and staying stuck. At Miller Health, RMR testing is recommended selectively, where it materially influences clinical decisions (a chronic dieting history, suspected metabolic adaptation or persistent fat-loss resistance), and quoted separately to the Explore assessment.
HOW IT WORKS
A simple, fifteen-minute measurement
You arrive fasted and rested, having avoided food, caffeine and exercise that morning, so the reading reflects your true baseline
You sit or recline quietly and breathe normally through a lightweight mask or mouthpiece for around ten to fifteen minutes
The device measures the oxygen you consume and the carbon dioxide you produce, the direct signature of your metabolism
Your dietitian interprets the result against your DEXA and blood data, then sets your fuelling targets accordingly
WHO IT IS FOR
When the test earns its place
RMR testing is most valuable when an estimate is likely to be wrong or when fat loss has stalled despite genuine effort. We recommend it where there is a long dieting history, suspected metabolic adaptation, persistent fat-loss resistance, a significant change in body composition goals, or where precise fuelling matters for training. Where a calculator would serve just as well, we will tell you, and leave it out.
QUESTIONS
Frequently asked questions
Is an RMR test accurate?
Yes. It provides a direct measurement of energy expenditure, unlike estimates from calculators, which can be wrong by several hundred calories a day.
How do I prepare?
Avoid food and caffeine for around four hours beforehand, skip exercise that morning and arrive rested. Your dietitian will confirm exact instructions when you book.
How long does it take?
The measurement itself takes around ten to fifteen minutes, plus time to discuss what it means for your plan.
What will I learn from it?
Your true daily calorie burn at rest, whether your metabolism has adapted to past dieting, and whether you primarily burn fat or carbohydrate, which together set your fuelling strategy.
Is it always needed?
No, it is recommended selectively, where it materially changes the nutrition strategy, and combined with DEXA and bloods for full context.