Short answer: yes, if you're setting calorie targets for weight loss, building muscle or fuelling serious training. An RMR test replaces a calculator's guess with your real number, so every target built on it starts from the right place. It costs £60 at our lab near Knutsford.
If you've ever cut calories, stuck to the plan and seen nothing change, the starting number may have been wrong. Here's what an RMR test measures, how it compares with online calculators and who gets the most from it.
What RMR Is and Why It Matters
Your resting metabolic rate (RMR) is the energy your body uses at rest just to keep you alive: breathing, circulation, keeping your brain and organs running. It's measured in calories per day.
For most people it makes up the biggest share of total daily energy use, often around 60 to 70%. Exercise and daily movement are added on top. So if your RMR figure is wrong, your whole daily calorie target is wrong too.
Calculators vs a Measured Test
Online calculators and fitness apps estimate RMR from your age, sex, height and weight. They're built from averages across large groups of people, so they work reasonably well for the "average" person and less well for anyone who isn't.
They tend to be furthest out for:
- People with a lot of muscle, or very little
- People who have dieted hard or for a long time
- Very active people and endurance athletes
- Older adults, and women around the menopause
An error of 200 to 300 calories a day is easy to miss, and over weeks it can be the difference between progress and none. A measured test removes the guesswork by measuring the oxygen your body actually uses at rest.
Who It's Worth It For (and Who It Isn't)
| You are… | Worth it? |
|---|---|
| Trying to lose weight and progress has stalled | Yes: check the starting number before cutting further |
| Building muscle and want to eat enough to grow | Yes |
| An endurance athlete who often feels flat or under-fuelled | Yes: it helps set fuelling targets around training |
| Coming off a long diet and wanting to eat more safely | Yes |
| In midlife or around the menopause and noticing changes | Yes: calculators are often furthest out here |
| Just curious, with no plans to change your eating | Probably not: the number is only useful if you act on it |
An RMR test won't diagnose a medical problem. If you suspect a thyroid or other health issue, speak to your GP first.
What Happens on the Day
This is the easiest test we do. You lie still and breathe normally.
- Prepare. Come in fasted, ideally first thing in the morning. Skip caffeine and exercise beforehand, and avoid hard training the day before. We send full instructions when you book.
- Settle. You lie down in a quiet room and rest for a few minutes so your body is fully at rest.
- Measure. You breathe normally through a mask while we measure the oxygen your body uses.
- Results. We go through your number with you, compare it with what calculators predict for you and talk about what it means for your eating.
What You Get and How to Use It
- Your measured RMR in calories per day
- A comparison with calculator estimates, so you can see how far off they were for you
- A starting point for your daily target: we add your activity and training on top to give a realistic total
- A clear next step: whether that's eating a bit less, eating more to support training, or simply confirming you're on track
Your RMR also gives you a baseline. If you diet for a long period, or your training changes a lot, a retest shows how your body has adapted.
FAQs
Is RMR the same as BMR?
Nearly. BMR (basal metabolic rate) is measured under stricter lab conditions. RMR is the practical version, and the two figures are usually very close.
Can I have a "slow metabolism"?
Some people do burn less at rest than calculators predict, often after long periods of dieting. Others find their metabolism is normal and the calculator was simply wrong. The test tells you which.
Will the test tell me how much to eat?
It gives you the foundation. We then add your daily activity and training to give you a realistic daily target.
Do I need to be fit to do it?
No. You just lie still and breathe. Anyone can do it.
Can I combine it with a VO₂ max or lactate test?
Yes, but the RMR test needs to come first, while you're fully rested and fasted. Get in touch and we'll plan the visit with you.
Book Your RMR Test
Stop guessing your calories. Find out what your body actually burns, for £60, at our lab near Knutsford, Cheshire.
Book your RMR testQuestions? Email perform@injuryandperformance.co.uk or message us on Instagram @perform.180
