Part 1 of this series.
One last look at Ben Greenfield’s 3+ hour endurance tests might give additional insights into what I am thinking here. The original article and data is here (Rewriting The Fat Burning Textbook – Part 2: Why You’ve Been Lied To About Carbs And How To Turn Yourself Into A Fat Burning Machine.).
Throughout this entire 3 hour workout Ben kept his VO2/kg at around 35-37. That resulted in RER numbers from 0.73 to 0.76 which corresponds to between 76 and 90% of his energy coming from body fat stores. That’s exactly what I am referring to. The researchers deliberately kept the intensity at an amount that was appropriate for fat burning. Remember, Ben had a VO2max value of 61.1. So for this test, he was running at around 60% of his VO2max value.
It is interesting that the researchers chose the point that they selected. They chose to work Ben at a higher rate than his optimal point of fat burning. My guess is that they wanted to make his performance look better. Truthfully, he wasn’t completely fat burning for this. The optimal point would have been at 30.5 (or so) VO2/kg or close to 45% of VO2max. Not sure why they didn’t exercise him at that point?
But how did the VO2max test numbers compare to Ben’s endurance numbers? After all, that is the goal here. When Ben was at about 35 VO2/kg in his VO2max test that correlated to an RER of about 0.78. Ben performed slightly better during the endurance test because his RER at about the same VO2/kg was 0.73-0.76.
The consistency in the data shows it is possible to hold a rate of 60% of VO2max for a very long time. This, again, is due to being fat and not carb fueled. Ben could have probably gone on longer had he exercised at 45% of his VO2max (the test ended for time).
This data tends to validate Phil Mafetone’s methodology. What I can’t figure out was Ben’s heart rate. The chart shows RR BPM but the numbers are like 20-30.