Glucose higher in endurance athletes?

Yup, i guess puberty and pregnancy are the two times in life where insulin resistance is an actual normal physiologic adaptation (as opposed to pathological like diabetes) where both blood glucose is high and insulin is high. When your body cannot keep up with additional insulin output to offset the higher blood sugar levels, that’s where it can become a problem. Luckily once the darn placenta comes out, most people are in the clear although at greater risk of developing diabetes in the future. I am actually being induced on Monday so obviously far along and when I was being screened for gestational diabetes, I failed by a close margin the first glucose challenge test. That made me have to do the elongated 3 hr glucose tolerance test and i passed that one with flying colors, in fact was hypoglycemic at the end. What a journey pregnancy is…


Post-Exercise Carbohydrate-Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults - PMC.

“This is the first study to demonstrate that post-exercise feeding to replace the carbohydrate expended during exercise can attenuate glucose tolerance and insulin sensitivity the following morning. The mechanism through which exercise improves insulin sensitivity is therefore (at least in part) dependent on carbohydrate availability and so the day-to-day metabolic health benefits of exercise might be best attained by maintaining a carbohydrate deficit overnight.”

The post-exercise paradox of reduced glucose tolerance and insulin sensitivity

“To conclude, the post-exercise paradox of reduced glucose tolerance and insulin sensitivity should be considered as a potential consequence of a pronounced metabolic adaptation to regularly performed endurance exercise. It is a transient phenomenon which demonstrates the complexity of the coordination of insulin-dependent and insulin-independent glucose and fatty metabolism in skeletal muscle and serves more investigation to fully understand the underlying mechanisms and potential consequences.”

The reduced glucose tolerance was seen most drastically in the group that did a 3 hour endurance ride. These are acute effects though, and I assume over time the training will improve sensitivity.


Thanks for sharing that linkThese 3 or so hour endurance rides (with efforts) are my bread & butter with my friends A couple of times a week as well as solo longish rides. Always got some protein and carbs in after the rides. Result - Diagnosed with Pre-diabetes at the end of last year. I’ve continued with the protein but stopped the carbs after the ride and together with one or two other nterventions it would appear that so long as I carry on as i am doing my glucose is back more or less where it should be. So much for the Golden Hour after excercise. The recent podcast guest Dr. Kyle Pfaffenbach’s advice seems to be right “I could care less about carbing up after a session, but make sure you get the protein in”


I’m reading that study as an argument against dieting on the bike. But it would be interesting to see how it fits with the larger body of literature on this topic

I still eat on the bike but as my ftp is a somewhat below elite levels, its no where close to even 90g/hr. It’s after the ride I’ve stopped putting in carbs unless it happens to be one of my normal meals.

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100 watt ave power will be about 360 calories or 90g of carbs. I guess you aren’t burning 100% carbs (probably) but still…for your 150 watt per hour ride you literally can’t take in as many calories as you are burning while exercising.

I do wonder about the post ride carbs though…we all need continuous glucose monitors to understand what the heck is going on.


I don’t know what you base your numbers on, but 100w should be, for most on this forum at least, be mostly fat. If you fuel that with 90g of carbs/hour you are definitely messing up something with regards to you glucose.

90g carb/hour starts, for me, at sustained (multiple hours) of 200+ watts.


I agree. I wasn’t clear . I fuel with nothing like 90 g / HR . 30-50g/HR depending on intensity. I was being sarcastic saying I was somewhat below elite. I’m a long long way from that.

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It’s never over 50% fat…or is it?

It’d put your 90g/hr starting at 200 watts just right, even if 50% is from fat.


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Worth listening to this Inside Exercise podcast if you want a greater understanding what is going on: Spotify

Just got some results back… 5.8 A1C. Kind of at a loss. Guess ima be cutting carbs

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Just confusing myself more. Here is one nugget:
" We also assessed continuous blood glucose profiles in world-class endurance athletes and found that they had impaired glucose control compared with a matched control group."

That’s fun. Their discussion has important points for interpreting this paper if you are a lay person:

we do not see a high risk that people wishing to improve their health through exercise enter the state of mitochondrial impairment and glucose intolerance due to ET volumes

The negative metabolic effects of excessive exercise found in this study are likely reduced as soon as the training load decreases. Indeed, we found a substantial improvement in metabolic parameters after only 1 week of reduced training in the RE compared with the ET phase.

From a health perspective, we do not advise against intensive exercise training as former elite athletes have lower mortality rates and seem to live longer compared with the general population

My additional (non-methodological-focused) personal comments would be:

  1. This study is focused on the metabolic situation that’s happening during overreaching/overtraining. I would have assumed that there would be altered glucose utilization during this based on what else we know about that syndrome, so these results don’t surprise me. It does make me wonder whether you could use CGM to help identify when an athlete was starting to enter non-functional overreaching territory, so that could be an interesting application.

  2. The “significant” difference in glucose control they saw in elite athletes is statistically significant. When you look at the actual degree of difference and what their glucose values actually were, it is extremely unlikely that this is clinically significant from a health perspective.

  3. Diabetes is a disease of insulin deficiency, not a disease of high glucose. We just use glucose values as a surrogate marker of the insulin situation because they’re easier to measure. It’s not clear to me that the normally assumed relationship between glucose and insulin that allows us to use it as a surrogate marker, is still present in well-trained endurance athletes. Ie: high glucose in overtrained endurance athletes is not the same thing as high glucose in an insulin deficient diabetic.

Maybe it just causes a different disease, called cnidosism, that makes you argumentative on the internet.


As a scientist, instead of relying on statistics I often rely on what the data actually looks like. I don’t feel the difference is very impressive in practical terms:

I’m not concerned.

extremely unlikely that this is clinically significant

We can go further: it is not clinically significant.


Thanks guys lol