Zach Bitter – Another FASTER participant

Zach Bitter was 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.).

Zach wrote about his experience in the FASTER study (Takeaways from the FASTER Study) where he gave some additional information about the FASTER tests. At least in Zach’s case (and probably in FASTER10 as well as FASTER43) the termination condition was inability to continue.

During the test, the researchers gradually increased both the speed and incline on the treadmill until I could no longer continue, and my rates of fat and carbohydrate metabolism at various intensities were measured.

Zach continued:

I can pinpoint where my fat metabolism and carbohydrate metabolism peak at varying intensities, and I can see the ratio between the two at any given percentage of my VO2 Max.

Zach had a very nice maximum fat oxidation rate and a very high rate of fat usage at a much higher % of his VO2max.

My fat metabolism peaked at 1.57 grams/minute. At this point in the test, my VO2 uptake was at 49.4. By dividing this number by my eventual VO2 Max of 66.1, I can calculate at what intensity I burn the most fat: 74.4%. At that intensity, I was burning 98% fat 2% carbohydrate (1.57 fat grams/minute and .07 carb grams/minute).

% VO2 Max
Fat Usage
Carb Usage

What  Zach is saying is that at 74.4% of his VO2max he is burning nearly 98% fat (his chart shows that point as 75%). We don’t have the rest of the data to see where he was in lower intensities. That may well be a product of his level of training? Clearly he was very fat adapted as well.

Zach’s 50-50% cross-over point (where he burned 50% carbs/50% fat) is much higher than mine. My crossover point was at 75% of VO2max. By my calculations, Zach’s cross-over point was 89% of his VO2max.

My own max fat oxidation was at about 50% of my VO2max where at Zach’s was 50% higher.

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