Tuesday 11 December 2012

Fat burner

So, I went for a couple of tests to take a look at fuel burning, how it works for me right now and any other information that comes with all of that.  At Cadence Performance, I had an RMR test and steady state analysis.

First up was the RMR test.   This measures the amount and types of gases I breathe in and out for a 15 minute period of sitting quietly.  For this, I was strapped into the gas mask and left to sit alone for 15 minutes without distractions while the data gathering appliance clicked, whirred and wheezed rhythmically at me.

Attractive attire, no?
There are guesstimate formulae you can use to work out an approximation of your RMR, based on weight, height, age etc. and using those formulae (and my weight of 62.6kg on that day) the prediction came out at 1400kcals.  What Peter (the sports scientist doing the testing) also said was that at rest, most people show a reasonably clear bias towards either carbohydrate burning as a fuel or fat burning.  And the results would soon show that both the estimated RMR and prediction of a strong bias were both wrong.

Remember, this test measures the actual air going in and the waste gases coming out after my body after there's been processing going on in there.  It is the best measurement you're going to get of what kind and quantity of chemical reactions are going on when you breathe.

RMR results...
MODE - Seated
PROTOCOL - Fasted/15 minutes

You may be at a LOWER RISK of gaining weight in the future than someone with a
lower RMR.  You may experience less than expected difficulty in reaching and/ or maintaining a healthy weight.
Respiratory Quotient (fat vs carbs) results...
RQ - 0.85 
EXPECTED RANGE (0.80 – 0.90)
Your RQ score is within the EXPECTED RANGE, you appear to burn Fat and Carbohydrate for energy in the expected manner while at rest. To maintain a healthy weight follow a meal plan LOW in total fat and HIGH in complex Carbs.

Your body prefers to burn CARBOHYDRATES for energy while you are at rest. You should consider a LOWER FAT diet to reduce potential weight/fat gain. If you want to maintain or lose weight it is ESPECIALLY important for you to follow a meal plan LOW IN TOTAL FAT and HIGH IN COMPLEX CARBOHYDRATES. No more than 20% of your total calories should be from fat. Higher fasting RQ’s have been linked to a tendency towards overweight regardless of an Average, Faster or Slower Resting Metabolic Rate status. Some studies suggest that people who are ‘CARBOHYDRATE BURNERS’ tend to conserve fat and over time gain weight faster than ‘ FAT BURNERS’. In one weight loss study people were more likely to lose weight if they had a lower RQ score.

LOWER RANGE: ‘FAT BURNER’ (0.70 – 0.80)

Your body prefers to burn FATS for energy while you are at rest. You should consider a LOWER CARBOHYDRATE diet to reduce potential weight or fat gain. You may increase the amount of fat you eat to approximately 30% of total calories, if desired. However, for health reasons you should limit the amount of saturated fat you eat.

So.  The test shows that A. my basic metabolic rate is almost 200kcals per day higher than estmated - i.e. "faster" and B. I am neither way strongly biased with fuels burnt at rest.  What is fairly amusing to me to read is that everyone, regardless of results, is advised to limit fat intake; even fat burners!  And the mid-range RQ scorers are still advised to eat a diet high in carbohydrates.

On to the steady state analysis.  This involved sitting on my bike on a turbo trainer to warm up a bit, then ramp through progressively higher resistances and measure outputs of gases, power and heart rate.

Pushing 180W I couldn't maintain 90rpm cadence, until I was pushed to thrash it.

At this stage you can get some headline results, like the fact that even at a reasonably thrashy effort level at the end, I didn't go anaerobic (my % fuel from fat was still around 25%) and my highest lung intake was over 3L/min of oxygen, giving a VO2 at the time of 48.5 (so my VO2max would be a bit higher than that, but no idea what without testing for that with a different test protocol than today's test).  And that's pretty much it for the day.  Cup of tea in the Cadence Cafe, staring at the cakes and feeling weird that they weren't desirable (despite the fact that they were beautiful and well-made from good ingredients), and back home again to wait a few days for the results.

The results are nice - raw data from the tests and some bits of analysis.  So I've created some graphs from the test so you can more easily see what's going on.

First up is the graph showing O2 in vs CO2 out and the two graphs chasing each other in parallel, not crossing at any point in the test - showing that I didn't hit my anaerobic threshold.

Also of interest to me was the volumes of gases circulating...

I particularly like the kcals burnt vs. heart rate, showing that when I spiked cadence at one point, my heart rate didn't spike with it, but my kcals burned did.

Now for the really interesting bit, and the part that I was really here for.  The splits in fuels burned... (again ignore the spike at the end as that's when the mask came off).  There's a marked change in gradient at 11.5ish minutes into the test and then the last 3 minutes or so are roughly stable.

Looking at the individual graphs of % of each fuel vs. heart rate and I have a really nice picture of what's going on at the moment.  See especially the last 3 minutes of the test, where my heart rate climbs dramatically as I push the highest wattage I can for a minute or so and the split between fat and carbohydrate burning doesn't really change.  It stays stable at around 75% carbohydrate and 25% fat. (again there's an erroneous spike at the end of the test when the gas mask was removed).

And the fat% vs, heart rate graph shows it slightly differently but clearly there's some sort of threshold crossed at the 11.5ish minutes mark when fat % drops dramatically before slowing and then stabilising at 25% to the end of the test and the mask being taken off.

I think that's jolly good information.  It shows that I may well have an engine designed for endurance sports - which is rather handy - and that it might have a decent capacity in there.  VO2max testing will give more of an answer on that one, but for now I have a good answer to the "am I fat burning yet?" question.  And the answer is an emphatic "yes".

Re-test in a few months to see what/if there are changes and I'll be interested to see what they are, or not.


  1. Very interesting!

    Can I ask where this place is and how much it costs, please? Also, do they do similar things for running, or would I have to jump on a bike (not a problem)?

  2. Ben - there are plenty of places that will do this sort of testing, I happened to go to Cadence Performance in Crystal Palace (opposite the athletics centre on Anerley Hill). Depending on whether you're getting a full VO2, sub-max or steady state test, you can expect to pay around £100 for that and another £50 or so for the RMR test which takes a lot less time.

    Usually, if you get the tests done not at a cycling centre, you'll get tested on a treadmill rather than turbo trainer. This will give different results as you have different efficiencies between the disciplines and use different muscle groups in different ways. Generally the HR for cycling will be 7-10BPM lower than for running, for example.