It’s taken me longer than I wanted to finally sit down and write this post, but whatever, you get what you pay for. It’s a longer post, and hopefully everything makes sense. Keep in mind I have no formal education in exercise physiology, so my interpretations of the testing/results may be wrong (although, let’s be honest, that’s highly unlikely – I know everything – just ask my wife).
I had the metabolic test done at a local tri shop. After filling out some basic health information (height, weight, age, etc) and signing my rights to sue should I die on the treadmill, the testing began. The testing was broken up into two parts, and I had to wear a neoprene face mask throughout. The mask was hooked up to some hoses, which fed into the New Leaf metabolic testing system. I specifically sought out a facility that used the New Leaf system, because the system creates a special profile that can be uploaded to a Garmin watch (more on that further down the post).
The first part of the test gathers my resting metabolic rate (RMR), or basically how many calories I burn if I were to literally do nothing but lay in bed all day. I basically just had to sit down for 15 minutes and breathe normally. It was real tough, obviously. You can’t eat or drink (except water) for six hours or so leading up to the test, but since mine was scheduled for 6am that wasn’t an issue. My understanding of the New Leaf system is that it essentially measures the concentrations of oxygen and carbon dioxide that your expelling, compared with the ambient concentrations. From that data, the number of calories that your burning, as well as the source of those calories (glycogen or fat) can be calculated.
The second part of the test is a little more fun, and a lot more work. I was asked what my 10k race pace was, which I had to guess since I haven’t raced a 10k for years. But since I knew my recent 5 mile pace, we just bumped that a little to get my 10k pace. After a short warm-up, the testing began at a 10:00/mile pace. 60 seconds later it was sped up to 9:00/mile. Then 8, then 7, then 6. After 60 seconds at 6:00/mile, they added incline. First 2% for 60 seconds, then 4%, then 6%, and I finally crapped out after 60 seconds at 8%. Here’s a video from the test (I sped it up, otherwise it would have been incredibly boring):
On the treadmill, you run a little bit past the point when the machine detects that you are no longer burning any fat, and that all of the calories you’re burning are coming from glycogen. That point is essentially your anaerobic threshold.
My daily calorie requirement, without any exercise, is 2704 calories. This factors in very minimal activity during the day – essentially walking to/from the bathroom, sitting all day long, etc. In order to just keep my organs running, and not have my body start breaking down muscle for fuel, I need to consume at least 2087 calories. So if I wanted to lose fat, eating 1500 calories/day would be unproductive in the long run, since my body would need to eat away at my muscle.
As for running (obviously the most important!), here are a couple of graphs I put together (nerd alert!) to illustrate some of the data that I was given.
I love that the New Leaf system gives me the fat calories burned along with the total calories burned. This will be most helpful during endurance events (like ultramarathons) so that I know how many calories I actually need to replace to avoid bonking. I have a limited supply of glycogen stored in my body, but an essentially unlimited storage of fat (in terms of completing an event, anyway). I will need to take in the glycogen calories that I burn, but I don’t need to replace the fat calories during the event. From the graph above, you can see that my body is a fat burning machine at around 145bpm. Depending on temperature and how I’m feeling, that’s been right around an 8:00/mile pace for me lately.
There’s some other data that I was able to get from the results, including my heart rate zones and my anaerobic threshold. I’ll write more about my anaerobic threshold in another post. Maybe. For now, though, I want to get to the fun part of the results – seeing how many calories I actually burn while running.
The New Leaf system creates a profile that, when loaded onto a Garmin device, will provide a measure of calories burned that is about as close to accurate as you can get. I’ve always thought that my Garmin Forerunner 410 overestimated the number of calories I was burning. I wear the heart rate monitor religiously, which is what the 410 uses to determine calories burned (based on some formula involving your age, weight, and heart rate).
I decided to do a little experiment to see how far off it really was. I loaded the New Leaf profile onto my old Garmin Forerunner 305, and didn’t change anything on my 410. I then sync’d both devices to the same heart rate monitor, and logged a couple of activities to see the difference. I felt mildly like a d-bag running around wearing 2 Garmins, but something’s are worth the humiliation in the name of science.
The final results:
On any given day, between my bike commuting and lunch break runs, I’m burning a grand total somewhere between 3600 and 3900 calories. Bring on the (vegan) bacon!