Another Look at the Lambert Endurance Study

In this post I looked at a study on (Fat Adapted Athletes). I wrote the original post well before I had my own VO2max tests so I didn’t have a way to apply it to my own situation.

I found a link to a paper which is critical of the study (Asker E. Jeukendrup. High-carbohydrate versus high-fat diets in endurance sports.  Schweizerische Zeitschrift für «Sportmedizin und Sporttraumatologie 51 (1), 17–23, 2003).

The practical relevance of the improved endurance capacity at 62% VO2max reported by Lambert et al. [Lambert et al. 1994], however, is questionable since no endurance events are completed at these low exercise intensities.

I think this is a valid criticism of the work capacity of Low Carbohydrate athletes. There is a sweet spot where the diet is the most efficient.

However, in its favor the Low Carb diet lowers the RER and increases the VO2max point where carbs are oxidized. In my own VO2max testing, my RER crossed over the 0.7 line (From 100% fat burning just starting into burning carbs).

My own crossover point was about 59% of my VO2max which is quite close to the point noted above. That is a sweet spot since it has as high of possible fat oxidation with zero carbohydrate oxidation.

It is probably true that there are few competitive sports where operating at this point offers an advantage. Endurance activities of the Long/Slow sort may be an exception, particularly in long ultra-marathons.

In theory, a fat adapted person could perform very long activities at this level. This number is essentially the MAF number in my case. But that’s partly because I am already fat adapted.

What does this look like for the vegan FASTER study participant? His VO2max was an impressive 63.4. So, 63% of that is 39.9. At that value Damian’s %CHO was 88%.  That means 88% of Damian’s energy was coming from carbohydrates. That puts him at a performance advantage if the activity is within his carbohydrate stores but a disadvantage if the activity for a longer time where he needs to access his fat stores.

It’s also an interesting discontinuity in his data at the next point. There his VO2max dropped and his carbohydrate oxidation went way up. Not sure if this was a walk/run transition. Perhaps Damian is a much more efficient runner than fast walker?

I would say that it seems pretty clear to me Damian is not very good at burning fat. His RER never gets below 0.85 which is a mixed fuel mixture. Not sure how low a dietary fat level he is normally at?

Damian’s MAF Number

Damian was 32 years old. His MAF is 180-32 = 148. Unfortunately, there is no Heart Rate column in his data and I can’t figure out what the correlation to the RR BPM column means.

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