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Active Metabolic Assessment Results Part 2

Friday, December 23, 2016

Continued from my last blog...

I got the results of my active metabolic assessment from the gym today. It was a test that scientifically measured my real metabolic response during various levels of exercise intensity. I wore an oxygen mask that looked similar to this one, and was hooked up to a computer to record my VO2 max and fat burn:


I performed my test on an elliptical machine. Starting at the lowest setting, every 2 minutes I increased the resistance while breathing through my mouth into the mask. At every interval, I was asked to rate how hard I felt I was working on a scale of 1-10. We ended the test when I said I reached a level 9, which was around 20 minutes with level 18 resistance (out of 20). At that point, I could not complete another 2 minute interval and maintain the same pace (about 4mph).

I started a cool down to lower my heart rate while my trainer went to make printouts and interpret my results.

So how did I do?

In a nutshell, pretty well. I may not be a top performance athlete, but I am healthy and in good cardiovascular health.

Here were my results (refer back to my previous blog for the meaning of the zone levels):

Heart beats per minute (bpm)
Zone 1: 113-153
Aerobic Base: 154
Zone 2: 154-162
Zone 3: 163-178
Anaerobic Threshold: 179
Zone 4: 179-186
Zone 5: 187-206

Fat/Carb Burn - Calories per Hour
Zone 1: 51%/49% - 450
Zone 2: 41%/59% - 498
Zone 3: 38%/62% - 576
Zone 4: 0%/100% - 642
Zone 5: 0%/100% - 756

As you can see, once I hit my anaerobic threshold in Zone 4, I am no longer burning fat. Glucose and/or glycogen is only being burned. Even though I am burning a lot of calories, none of it is coming from fat.

My trainer said my fat burn in Zone 1-3 is very good. What she often sees in her clients is they only burn fat in Zone 1, and it disappears in Zone 2 and 3. This means a metabolic crash, either through chronic cardio or a bad diet. The body can't burn fat when it is under stress or inflammation.

In my case, my body is burning both fat and glucose. Note that I am not currently under a keto diet, but I am likely fat-adapted more in the Mark Sisson primal sense: I can use a mix of either fat or carbs for fuel. The test seems to confirm that.

"[A] fat-burning beast will be able to burn glucose when necessary and/or available, whereas the opposite cannot be said for a sugar-burner. Ultimately, fat-adaption means metabolic flexibility. It means that a fat-burning beast will be able to handle some carbs along with some fat. A fat-burning beast will be able to empty glycogen stores through intense exercise, refill those stores, burn whatever dietary fat isn't stored, and then easily access and oxidize the fat that is stored when it's needed."


Note that this does not mean I am eating a high carb diet. My diet is still low carb compared to SAD. I have been eating a slightly higher carb load due to the holidays (stuffing, mashed potatoes, pie, cookies), but I stay under 130g as my personal max tolerance. I try to average 60-80g carbs per day, but I haven't been tracking diligently lately.

(It would be very interesting to compare if I took the test again after switching to keto adaption for a few months. The test is pretty pricey, so that won't be an experiment that happens soon).

My V02 result came back in the 'optimal' range for my age. VO2 means "Volume of Oxygen". VO2 is the maximum amount of oxygen your body can use at any time. The higher your VO2, the more oxygen your body can use, and the better your endurance and stamina during exercise. A high VO2 means your heart is healthy and pumping blood and oxygen efficiently. A higher VO2 correlates to a lower risk of cardiovascular disease.

Because I burn fat in Zone 1-3 which is expected in a healthy metabolism, my trainer has given me a program where I have some intervals in the anaerobic threshold with most in the aerobic ranges.

If my fat burn stops in anaerobic, why do it at all?

Referring back to the Zone definitions, Zone 4 increases peak VO2 and anaerobic thresholds. Occasionally pushing the anaerobic threshold makes the heart have to adapt and work better. This will eventually cause my heart rate to climb slower, and fall back to base levels during rest faster. The result: higher endurance.

The goal is thus we're attempting to tweak my program so I increase my workout endurance, get stronger, and reduce fat! Win, win, win!

I am doing a 5 day structured workout program. All workouts start with a 15 minute warmup where I gradually raise my heartrate to my "base" at 154 bpm.

Monday: Peak Zone 4 high intensity interval training (HIIT). 8 sets of 1 minute intervals. Heartrate 179-186. 1 minute recovery between intervals.
Tuesday: Resistance Training
Wednesday: Base Fat Burn Zone 1-2. 30 minutes. Heart rate up to 162.
Thursday: Resistance Training
Friday: Zone 3 moderate intensity interval training (MIIT). 4 sets of 4 minute intervals. Heart rate 163-178. 1 minute recovery between sets.
Sat/Sun: Recreational and/or rest day.

I am doing this for 4 weeks, and then we will follow up. In about 3 months, I'll get tested again to see how things have changed. If all goes well, my max heart rate should go lower, and my anaerobic threshold should go higher, which means I will burn fat for longer.

I've always been curious about how my real body behaves compared to the so-called 'fat burning zone' on the machines.

How do my real tested numbers stack up against the theoreticals?

According to the formula, max heart rate is 220- (your age). In my case, 178.

My real heart rate max is 206. 178 is the start of my anaerobic threshold. I recommend researching ways to estimate your heart rate max other than this formula. Getting your heart rate zones estimated is very important if you want better results with your goals.

The online calculators say I should burn 539 calories if I exercised on an elliptical at a moderate pace for 60 minutes.

My tested values say I burn 576 calories in 60 minutes if I kept a pace in Zone 3 for the duration.

My takeaway? Yes, the estimates and calorie calculators are off, but not by a million miles. They are good enough to approximate for most people. The most important thing is just to do it.

Main takeaway is more intense exercise is not necessarily better for weight loss. Strenuous exercise is very good for improving cardio health, but not too much. I've said for a very long time that walking is the best weight loss exercise there is, and my personal test results have confirmed that. Low to moderate exercise is a winner. Get a FitBit and walk, walk, walk to a healthier, trimmer you!

This was one of my most interesting and informative experiments I've done yet. I hope it has given all of you something to think about as you set your 2017 goals.

Merry Christmas, and good health to you in the New Year!
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Member Comments About This Blog Post
  • SBEAR5
    This is very interesting. Thanks for sharing your results with us! I may look at where I can do this in the future. I don't seem to have much luck losing weight with exercise, this test may help me to alter that. And like you, in the past I have lost weight with just walking.

    Thanks for the "deep thoughts" material. haha :)

    1486 days ago
    great info you got there, I've always taken the calorie burn estimates with a grain of salt, and just pretty much go with my own personal data sets, either from my fitbit or previously my HRM.
    1488 days ago
    Very interesting and I am happy to hear that your fat burning zones was 1 - 3. That gives me hope since I pretty much can't get to the zone 4 or 5 intensity. Thanks so much for the information.
    1489 days ago
    Interesting. I'll be interested to hear how you do in three months.
    1489 days ago
    Definitely some interesting data there. Thanks for explaining and sharing.
    1489 days ago
    This is such awesome information! It explains a lot about how folks can do so much exercise and still not burn the fat that they want to lose!
    1489 days ago
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    Disclaimer: Weight loss results will vary from person to person. No individual result should be seen as a typical result of following the SparkPeople program.