The main test that Ben test was a three hour treadmill test in the FASTER study (Jeff S. Volek, Daniel J. Freidenreich, Catherine Saenz, Laura J. Kunces, Brent C. Creighton, Jenna M. Bartley, Patrick M. Davitt, Colleen X. Munoz, Jeffrey M. Anderson, Carl M. Maresh, Elaine C. Lee, Mark D. Schuenke, Giselle Aerni, William J. Kraemer, Stephen D. Phinney. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism, Volume 65, Issue 3, March 2016, Pages 100-110.).
In Ben Greenfield’s case the activity was done at an average of 60% of VO2max. At that level of effort Ben got 85% of his energy from fat and 15% from carbohydrates. Here’s the data from the three hour treadmill test.
| %VO2max | FATcal | CHOcal | %cal-fat |
| 58% | 10.013 | 3.1007 | 76% |
| 61% | 12.394 | 1.2341 | 91% |
| 59% | 11.722 | 1.4985 | 89% |
| 60% | 11.645 | 1.8409 | 86% |
| 61% | 11.154 | 2.5325 | 81% |
| Average = 60% | 11.386 | 2.046 | 85% |
An interesting question is the trend of the oxidation over the three hours. Here the graph of the data is interesting. The blue line is energy from fat and the brown line is energy from carbs. The x-axis is time. Note that as time proceeds Ben is drawing less and less energy from fat and more and more from carbohydrates. The R^2 values show a strong significance.
Ben’s individual Fat Oxidation data is not too far off of the data from the study. The average makes it look as if a person could continue on seemingly forever but Ben’s data shows that is not the case.
Similarly, his carb oxidation rate is very similar to the average since it shows a steady climb up.
It should also be recalled that although fat provides 9 calories per gram and carbohydrates provide 4 calories per gram fat is burned less efficiently for energy – about 10% less efficient than carbohydrates.
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