THE TRUTH ABOUT CARBS FOR CYCLISTS | Dr. Kyle Pfaffenbach | Ask a Cycling Coach Podcast 528

Ask a Cycling Coach Podcast
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While not frequent, it isn’t uncommon for us to receive questions from athletes reporting a high A1C and their medical advisors suggesting it could be from their high carbohydrate intake on the bike.

This can be alarming, scary, and is a topic that requires thorough examination. Sooo, we put up the bat signal for Dr. Kyle Pfaffenbach :slight_smile:

Kyle did a fantastic job of breaking down carbohydrate metabolism, insulin dynamics, context and fundamentals of A1C, and how all of that is understood in the context of endurance athletes that regularly carry a consistent training schedule and those that take in high amounts of carbohydrate.

Give it a full listen and share this with your friends any time they express concern about this topic!

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(00:00) Welcome!

(00:28) Is High Carb Intake Making Cyclists Diabetic?

(04:00) Carbohydrate Metabolism Deep Dive

(08:22) Insulin’s Role in the Body

(11:19) The Impact of Diet and Lifestyle on Insulin Resistance

(15:36) Scientific Insights and Research on Insulin Sensitivity

(24:40) Understanding Glycogen Depletion and Flux

(26:15) The Role of A1C in Diagnostics

(29:46) A1C and Cyclists: Contextual Considerations

(33:32) Impact of Carbohydrate Intake on A1C

(45:09) Balancing Diet and Exercise for Cyclists

(49:50) Concluding Thoughts and Recommendations

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Super timely for me as my A1C has bumped up to high pre-diabetic range and I’m trying to figure out how to modify my consumption while still fueling training. Thanks!

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Glad the timing worked out so well!

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Not a doctor but I recently learned about exercise-induced hemolysis and its impact on a1c.

From my Gemini chat history,

A1c in Endurance Athletes: Unique Considerations

Endurance athletes can sometimes present with A1c levels that might be unexpected for their generally healthy metabolic profile. Here’s why:

  • Increased Red Blood Cell Lifespan: Some individuals, including potentially endurance athletes, may have a longer average lifespan of their red blood cells. Since A1c reflects the accumulation of glucose on hemoglobin over the lifespan of the red blood cell, a longer lifespan means hemoglobin is exposed to glucose for a longer period, potentially leading to a higher A1c even with normal average blood glucose levels.

  • Hemolysis and Red Blood Cell Turnover: While less clearly defined, increased red blood cell turnover due to hemolysis could theoretically affect A1c levels. However, the impact is complex and not fully understood. Some studies suggest that conditions with increased red blood cell turnover might lead to lower A1c values because younger red blood cells have had less time to be glycated. Conversely, if only a subpopulation of older red blood cells are preferentially destroyed, the average age of the remaining cells might be lower, potentially influencing A1c.

Important Considerations for Endurance Athletes and A1c:

  • A slightly elevated A1c in an endurance athlete without other risk factors for diabetes should be interpreted with caution. It doesn’t automatically indicate prediabetes or diabetes.
  • It’s crucial to consider other markers of glucose metabolism, such as fasting glucose, oral glucose tolerance tests, and continuous glucose monitoring, to get a more complete picture.
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Same here this time last year. I’ve just learned that a fasting insulin level test, if I can get one, is a better indicator of whether I am actually pre-diabetic or not.

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Outstanding episode! Thank you so much for posting it. As a former diabetic, some of the material was a recap of my previous studies, but it was great to have it laid out in such a concise format. Also picked up a few new concepts and specifics I either didn’t know or had forgotten.
Kudos and thank you!

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Excellent podcast!!! Very good information debunking a lot of misinformation that flies around the internet (and sometimes this forum).

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Only half way through but to echo what as already been said. What an outstanding episode. Definitely one to listen to a few times. Should be compulsory listening here in the UK for GP’s and Practice Nurses.

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I’m SOOO excited about this episode. Never been more excited about an episode.

I have to re-start the podcast, though. My simple brain couldn’t follow the answer to the first question.

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One thing to point out (I’m not sure if the episode addresses it), do not trust a diagnosis of diabetes or pre-diabetes based on a blood test that was NOT done while fasting. Only a fasted blood test is going to be accurate enough to not be a false positive.

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Yes, it was discussed

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Great episode. One of the best presentations on the topic I’ve heard. Just enough of a deep dive to get a basic idea of what’s going on. Complex topic explained in a way normal people can understand.

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If you’re going to eat donuts, eat them on the bike.

Roger that.

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Be nice to do one of these for saturated fat.

I’ve wondered if eating a high saturated fat food mid ride is as bad for you as if you’re on the coach…like do you “burn it off”.

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I think you could ‘burn it off’, but the question then becomes what type of ride are you doing, and what dirt of performance are you expecting? The fat won’t burn as readily, so you’d probably need to dial back your intensity if you ride goes over an hour, or two. Additionally, our bodies already store plenty of fat, so I don’t think that consuming fat during a ride would provide any particular benefit.