Endurance athletes and Hb A1c

[Marbles]

Until recently, I was not aware of most of the below, and I doubt many providers are as it applies to a small subset of American society. But, probably a much larger subset of RS, so I figured I would share it here and perhaps save someone else some stress.

At my recent well check my A1c was in the American prediabetic range at 5.8%. I'm also over weight by BMI, but not over fat by Dexa scan (19.2% body fat). So, at an office visit I look like a higher risk individual than I am and lifestyle modification was recommended (weight loss, exercise, diet improvement).

Endurance athletes commonly have Hb A1c's that are high by the American standards, but have excellent metabolic flexibility (not prediabetic, no metabolic syndrome).

The question becomes, does one have glucose regulation issues as this influences lifestyle recommendations. In the end accurate assessment, not denial, is the goal. Health care providers see a lot of denial, and the arguments in this post would certainly come across as such. So, the following things can clarify the clinical picture for both patient and provider:
-A normal fasting glucose argues against this (mine was normal).
-A normal fasting insulin argues against this (mine is normal, I had to request it)
-If my provider remains concerned, I will ask for a glucose challenge test as that gives the most direct assessment of glucose management in the body.
-A LPIR (Lipoprotein Insulin Resistance score) comes up, I'm not sure if it is validated in endurance athletes, and being an indirect measure used to assess risk it is of questionable value in any population it was not validated in.

The other difficulty is proper fueling as an athlete, which is driven by lots of carbs. The key here is full blown diabetes should consume carbs at the level recommended for none diabetes during exercise. So on heavy days 900+ grams of carbs (over 3500 calories of carbs) fall within my recommend consumption range.

The ADA (American Diabetic Association) is the only organization that recommends the 5.6% threshold on Hb A1c as being prediabetic, the rest of the world uses 6.0%. Athletes engaging in more that 300 minutes of moderat to high intensity cardio a week probably shouldn't be concerned until they are 6.0%.

The 300 minute cut point is based on intuition, there is not much hard data available on athletes when it comes to this topic. Anyone getting less than 300 minutes a week is leaving easy long term health gains on the table anyway, so increasing would be to their benefit regardless of if the Hb A1c is a sign of a problem or not.

 

[atmat]

It is not uncommon for a variety of reasons, most notably the higher rate of RBC turnover.

 

[Marbles]

It is not uncommon for a variety of reasons, most notably the higher rate of RBC turnover.

I think you mean reduced rate of RBC turnover. Higher rates produce artificially low A1c levels.




A side not of general interest, many people who write about this discuss "exercise induced insulin resistance" which is amusing as insulin secretion is known to decrease during exercise; and insulin sensitivity is known to increase during exercise. It is why exercise is so beneficial for type 2 diabetics and why type 1 diabetics have lower insulin needs during prolonged exercise.

It is true that athletes can have blood glucose that holds as high as 180 during exercise, but insulin resistance is not the cause (insulin resistance implies that glucose cannot enter cells for use), rather it is a well tuned metabolism that can poor on the fuel to sustain rapid consumption.

 

[ztc92]

Very interesting topic and one I wasn’t aware of. I don’t have much to add but I appreciate the insight in case I ever encounter this situation with patients, especially in the sports medicine world. I’ll be following along with interest.

 

[P Carter]

I’m probably missing something here, but if the recommendations are weight loss, exercise, diet improvement, those could very well be valid, even for a self-described “endurance athlete,” yes?

And it’s quite possible for self-described endurance athletes to be unhealthy, yes?

I do agree that the “normal” ranges need to be contextualized and understood, and I’ve been quite frustrated at what I perceive to be modern medicine’s focus on just checking the boxes without wanting to really dig in and understand an individual and what those numbers mean to that individual.

At the same time, I think people—self-described endurance athletes especially—tend to overestimate the health benefits of whatever they are doing.

 

[omicron1792]

See. I’m a believer that over exercise can be a risk factor in itself. I think the induced hypoxic stress on organs and the muscle breakdown byproducts can both be harmful.

 

[Poser]

I’ve had high, pre diabetic range, A1c levels for the last couple of years and they kept inching up slowly. I was very miffed by this as I was eating reasonably healthy and super active all of the time. I quit drinking entirely and that didn’t seem to make any difference over the course of 12 months.

Finally, I switched to 90% keto diet for 3 months + started supplementing Chromium, Alpha Lapoic Acid and Berberine and my levels dropped back into normal range within that 3 month window.

 

[Marbles]

I’m probably missing something here, but if the recommendations are weight loss, exercise, diet improvement, those could very well be valid, even for a self-described “endurance athlete,” yes?

And it’s quite possible for self-described endurance athletes to be unhealthy, yes?

I do agree that the “normal” ranges need to be contextualized and understood, and I’ve been quite frustrated at what I perceive to be modern medicine’s focus on just checking the boxes without wanting to really dig in and understand an individual and what those numbers mean to that individual.

There is a reason why I brought up additional tests. As I said, denial is common, and not the goal, and yes, those can be valid recommendations for most, most of the time. To be clear, based on the information she had, her recommendations were very reasonable.

A summary of the points below:
-Weight loss, consider fat mass vs lean mass.
-Exercise above 300min/wk has minimal health benefits.
-Diet can almost always be improved, but how matters.

Below I use myself as an example because you are correct, this is complex. Hopefully it can help someone think through their own stuff.

On more exercise:
When a heavy week is 10+ hours of aerobic training, the recommendation to pile on more is dangerous. While not harmful, once 300 minutes a week are hit, increasing further brings very small health gains based on the available evidence. So, you go past 300 minutes a week for reasons other than health as the returns are too small to justify the investment.

On diet:
99.99% of use can improve our diet (and that includes me), the question is how. Under a heavy training load, cutting carbs is not an improvement; based on current evidence, it too would be harmful; especially if paired with increasing load.

On weight loss:
This is were a Dexa scan (or other highly accurate assessment of body composition) comes in. I listed body fat percentage above, but really FMI (fat mass index) is probably the best as adding muscle mass will lower the percentage, but is unlikely to make adding fat acceptable. A normal FMI is 3-6. Mine is 5.2. In my case, I would like too loose weight, but like adding exercises past 300 minutes, the long term health benefits are small at best. My reasons are improved performance and cosmetic.

If I dropped only fat mass, an FMI of 4 would still leave me over weight by BMI and would not meaningfully alter my metabolic health. An FMI of 3 would put me in the normal weight BMI. I look "gaunt" (to quote my wife) at that weight. For myself, I would be fine dropping a little muscle too, but I'm not going to engage in unhealthy behavior to do so, nor am I willing to cut out strength training.

A high (5.6-5.9) A1c with normal fasting glucose is very different than a high A1c with high fasting glucose. If the A1c is over 6.0 or up, then look hard for a pathologic reason (iron deficiency, liver issues, diabetes). For most healthy people, a few lab tests is enough.
-Normal CBC rules out iron deficiency
-Normal LFTs and protein argues the liver is fine
-Normal fasting glucose and/or fasting insulin strongly argues for normal glucose metabolism. A glucose challenge test would give the best assessment of glucose metabolism.

At the same time, I think people—self-described endurance athletes especially—tend to overestimate the health benefits of whatever they are doing.

There is some truth to this. It is one reason why I bring up additional assessments. Along the same lines, endurance athletes build up more coronary artery plaque than their non-enduance peers. This is not enough to undo the protection given by the endurance training (on average endurance athletes live longer), but it does suggest more benefits from good lipid control. Denial is ignoring genetically crappy lipid levels, and many people do this.

 

[Marbles]

See. I’m a believer that over exercise can be a risk factor in itself. I think the induced hypoxic stress on organs and the muscle breakdown byproducts can both be harmful.

Truly elite athletes (such as olympians) outlive non-elite peers. There are all kinds of confounders in there, but it pretty reliability puts to bed the idea that a lot of training is unhealthy long term.

 

[freezerfull]

Truly elite athletes (such as olympians) outlive non-elite peers. There are all kinds of confounders in there, but it pretty reliability puts to bed the idea that a lot of training is unhealthy long term.

The only over training concerns, most should worry about, more has to do with musculoskeletal wear and tear or acute injury.

I can only speak from my experience. Endurance is best built by doing the intended activity over the longest duration in a manor that is more difficult then when you do the goal activity. The reasons to do this have little to with cardiovascular and metabolic results, however both will be benefited immensely. I notice a substantial improvement in lipid panels and improved metabolic function, particularly weight loss, when I started doing longer duration endurance training activities more frequently. Example would be 3000’ gain hikes with 50lb packs 2-3x per week and a 6000’+ gain hike with 50lb pack (descent gets water dumped) at least 1x per month vs doing 7 hikes with 1000’ of gain and a 50lb pack each week.

 

[North of 60]

Thanks @Marbles...that is some good info.

 

[V2Pnutrition]

What a great (and uncommon) string to pull on in the thread of endurance training, @Marbles .

An issue I’ve seen pop up with athletes we have (and even patients when I was at the hospital) was that the intensity of their training didn't actually warrant such a high carb intake- even if the duration was long. Remember the recommended carb dosing is based on the idea that the muscle can turnover 1g of carbohydrate for ever 1 minute of higher intensity training or competition.

This used to be 60g for 60-min, but many guys have been pushing 90-120g per hour in an effort to illicit a better performance. Like most sports/hobbies, the gen-pop, weekend-warriors*** have tried to follow suit in their amateur ambitions of setting PRs for local races. But, their training often doesn't duplicate the intensity or the volume of the pro folks they're trying to mirror. As such, a large portion of carbohydrate remains in the blood since the muscle turnover isn't fast enough to justify that much of an intake.

When we're able to pull those down (60g every 2 hours for Z2 instead of 60-90-120g every 1 hour, for example), the blood sugar follows suit and comes into normal limits.

Another potential option there could be that the rise causing increased HgA1c could be blunted (or augmented) by mixing it with another macro (fats and proteins) to prevent such a dramatic increase in bg (adding in a Chomps stick- fats and protein- with your high-carb snack of choice).

Third is the ongoing stress of training. If it’s in the middle or end of a big block, I’d often tell folks to get it redrawn during a transition or off season to which it comes down.

I've seen the same with LDL and Total-C numbers too in the middle of big training blocks. When a person is actively losing fat, the fat cell liberates into a glucose and fatty acids. Excess liberation puts more fat in the blood and lab draws will pick up on that.

***I don't mean that in an inferior sense- more the fact that they're (myself included) not paid athletes with copious amounts of time on their hands to rack up 30-hours of training in a week...

 

[P Carter]

What a great (and uncommon) string to pull on in the thread of endurance training, @Marbles .

An issue I’ve seen pop up with athletes we have (and even patients when I was at the hospital) was that the intensity of their training didn't actually warrant such a high carb intake- even if the duration was long. Remember the recommended carb dosing is based on the idea that the muscle can turnover 1g of carbohydrate for ever 1 minute of higher intensity training or competition.

This used to be 60g for 60-min, but many guys have been pushing 90-120g per hour in an effort to illicit a better performance. Like most sports/hobbies, the gen-pop, weekend-warriors*** have tried to follow suit in their amateur ambitions of setting PRs for local races. But, their training often doesn't duplicate the intensity or the volume of the pro folks they're trying to mirror. As such, a large portion of carbohydrate remains in the blood since the muscle turnover isn't fast enough to justify that much of an intake.

When we're able to pull those down (60g every 2 hours for Z2 instead of 60-90-120g every 1 hour, for example), the blood sugar follows suit and comes into normal limits.

Another potential option there could be that the rise causing increased HgA1c could be blunted (or augmented) by mixing it with another macro (fats and proteins) to prevent such a dramatic increase in bg (adding in a Chomps stick- fats and protein- with your high-carb snack of choice).

Third is the ongoing stress of training. If it’s in the middle or end of a big block, I’d often tell folks to get it redrawn during a transition or off season to which it comes down.

I've seen the same with LDL and Total-C numbers too in the middle of big training blocks. When a person is actively losing fat, the fat cell liberates into a glucose and fatty acids. Excess liberation puts more fat in the blood and lab draws will pick up on that.

***I don't mean that in an inferior sense- more the fact that they're (myself included) not paid athletes with copious amounts of time on their hands to rack up 30-hours of training in a week...

Bingo - much better said than I could.

There seems to be a trend of self-describing as an "athlete." That's probably good to the extent it fosters structured training, more movement, etc. etc. But there are downsides--actual athletes are training far more than anyone really realizes.

It's very easy to think, "Hey, I've run a 50k, I don't need to think about what I eat." Or, "I ran 10 miles today, so I'm going to eat 75 Reese's peanut-butter cups to replace the extra 1,000 calories I burned." Or, "During my 2-hour run I'm going to pound 800 calories per hour and then eat an extra 75 reese's peanut-butter cups because I'm craving sweets." And then there's surprise when body comp changes, or bloodwork is out of whack.

For context: I have done, and continue to do, despite my best efforts, all of the above.

And I think it's absolutely true that a general practioner MD just tends to look at average numbers and make recommendations from there, rather than really consider the nuance of an individual.

Not looking to derail - just a thought.

 

[Marbles]

@V2Pnutrition and @P Carter


So, instead of repeating different variations of what I have already written, I'll field some questions that if I misunderstand the answer two would change my conclusion.

1. What is the badness that makes a prediabetic range Hb A1c a concern?

2. What is Hb A1c supposed to represent and why is the diabetic cut off of 6.5% more concerning than the prediabetic range?

3. Is there data to separate populations between 300 minutes of high intensity and 300 minutes of moderate intensity? (Using the standard definition where 3-6 METs is moderate and >6 METs is high). Is there any data to stratify within high intensity (say 8 METs vs 16 METs) or to point too METs being a better assessment than HR (is 8 METs at 15% of anaerobic threshold different than 16 METs at 15% of anaerobic threshold between individuals)?

5. What threshold counts as a lot of training?
Outside of cycling, even paid athletes are not doing 30 hours of high intensity work a week. Tom Evans was doing about 12 hrs/wk leading into his UTMB win last year. Aleksandr Sorokin was doing about 15 hrs/wk leading into his world record 100 mile run in 2022.

 

[P Carter]

First off, thanks for the discussion, I think it’s helpful. I’m not a healthcare professional, and don’t have a full understanding of all the studies in the area, and certainly am not suggesting how you should respond. Just noting a few things from my experience, and for context for those that might read the thread.

I think we actually agree on most things and are ultimately making slightly different points.

I agree that if a doctor or NP looks at numbers based on population data, and then makes canned recommendations that make you raise an eyebrow, definitely dig deeper. If the canned recommendation is, due to this single number, you need to eat less, exercise more, and lose weight, but you’re already exercising 5 hours a week, your BMI or other info doesn’t indicate a need for weight loss, then take those precise recommendations with a grain of salt; think critically; dig deeper.

I also agree that, at the same time, be wary of delusion – it’s very common to think “I’m different” or “that doesn’t apply to me.” If you find yourself thinking this, confirm that you’re not engaging in self-delusion.

Where I think we might part ways is the question: Is it healthy to have A1c numbers in the prediabetic range, so long as someone exercises more than 300 minutes a week and has an acceptable body fat percentage?

I honestly don’t know the answer to that question. But I’m skeptical that the answer to that question is: “Yes, it’s healthy, and if this happens to you, the best thing to do is continue without addressing it.” (I'm not saying that you are saying this - just an overall comment.)

I’m skeptical for a few reasons. First, self-described endurance athletes, including myself, likely overestimate the impacts their training has on their physiology. In know from my experience, I have historically—and continue to!—eat too many carbs and too much fat even when running between 5 and 12 hours per week. I know this because my body comp changes, my body fat % increases even though, in my head, I’m training so much that this could not possibly be happening. And I'm hungry all the time, so how could I be over-consuming calories when it feels like I'm in a calorie deficit? But it's happening.

Second, I'm skeptical that conclusions based on “endurance athletes” should be expanded to hobbyists. This addresses your question 5. I don’t know what the threshold is, or if there’s a precise number threshold. (Probably not.)

I do know that actual endurance athletes have different lifestyles than hobbyists. For example, my brother and sister ran track and cross country and D1 schools. They ran between 70 and 100 miles a week. The duration and intensity of those miles was carefully planned and monitored. The intensity of the workouts was very high. Like, 18 miles at sub-6-minute-pace high for the weekly long run and mile repeats at 4:30-minute-pace for speed work. I don’t know precisely how many hours they spent actually running. But alongside the running they did strength training; physical therapy work; extensive warm-ups and cool-downs for each run; conscious recovery; and other ancillary work. Their meals were planned with a nutritionist. They (mostly) never gorged on crappy food. They had periodic body-composition tests. If they weren’t hitting expected times--and expected times were calculated within minutes or seconds-- they’d consult with the coach, nutritionist, sports psychologist, etc. to figure out why. It’s very possible that they would have physiological markers that differed from the general population. Any conclusions derived from this legitimate endurance-athlete population just don't translate to me, even if I’m out there running (or, more accurately, jogging/walking) 5 to 12 hours a week.

For good measure, it’s also not entirely clear to me that markers derived from a legitimate endurance-athlete population are actually “healthy” for a 41-year-old hobby-jogger. The endurance-athlete population almost surely doesn’t have metabolic disease. At the same time, it’s not clear to me that their markers would be good indicators of general health. Seems like a highly stressed population: the goal is not overall health, but instead to apply as much stress as possible without suffering a breakdown. And breakdowns/injuries were very common.

Third, it’s my understanding that the data in this area is so sparse that it’s hard to draw actual conclusions from large-scale, peer-reviewed studies.

Again, I’m not an expert, and I do not know specific answers to questions 1-3. If Kyle weighs in, all ears!

Hopefully this clarifies where I'm coming from rather than derailing.

 

[V2Pnutrition]

@V2Pnutrition and @P Carter


So, instead of repeating different variations of what I have already written, I'll field some questions that if I misunderstand the answer two would change my conclusion.

1. What is the badness that makes a prediabetic range Hb A1c a concern?

2. What is Hb A1c supposed to represent and why is the diabetic cut off of 6.5% more concerning than the prediabetic range?

3. Is there data to separate populations between 300 minutes of high intensity and 300 minutes of moderate intensity? (Using the standard definition where 3-6 METs is moderate and >6 METs is high). Is there any data to stratify within high intensity (say 8 METs vs 16 METs) or to point too METs being a better assessment than HR (is 8 METs at 15% of anaerobic threshold different than 16 METs at 15% of anaerobic threshold between individuals)?

5. What threshold counts as a lot of training?
Outside of cycling, even paid athletes are not doing 30 hours of high intensity work a week. Tom Evans was doing about 12 hrs/wk leading into his UTMB win last year. Aleksandr Sorokin was doing about 15 hrs/wk leading into his world record 100 mile run in 2022.

I’m not sure I fully understand what you’re asking in some of the questions, but I’m happy to share my thoughts. I’m also definitely not trying to “change your conclusion..” - just giving input from my own experience in working with clients and athletes over the last however many years.

The very short answer to all of your questions is because you are you. Tom Evans is Tom Evans. Aleksandr Sorokin is Aleksandr Sorokin.

We have to take the data (labs, training, etc.) from an individual and work with what it’s telling you rather than what we think we should be seeing…even if it doesn’t make sense. If the HgA1c is high in spite of activity, diet, great VO2, etc., then it’s high and time to start figuring out why and how to get it down.

The diabetic range is not more important than pre-diabetic in my mind. Prediabetic is of concern because it’s suggesting the inevitable is on the horizon if a change isn’t made. If anything, prediabetic is of more value to me than diabetic because there’s an opportunity to change the course. I’m not waiting until it creeps into 6.5% territory to say “Oh man…that must’ve been true! Time to change…” I’m doing it when it when I see a creep up to 5.4%, 5.5%, 5.6%, etc…especially if that trend is over time.

I try to remind myself that factors aren’t mutually exclusive- you can have a great VO2 max, big training blocks and a high A1c- just like I’ve seen MANY “skinny” people who are walking time bombs by their lab values (cholesterol, cardiac markers, diabetes markers, etc…).

My uncle was a builder and always told me "trust your level, not your eye!" I've found it to not only be true in my carpentry, but also in my professional work. I don't trust "what it should be". I trust what it is.

 

[omicron1792]

First off, thanks for the discussion, I think it’s helpful. I’m not a healthcare professional, and don’t have a full understanding of all the studies in the area, and certainly am not suggesting how you should respond. Just noting a few things from my experience, and for context for those that might read the thread.

I think we actually agree on most things and are ultimately making slightly different points.

I agree that if a doctor or NP looks at numbers based on population data, and then makes canned recommendations that make you raise an eyebrow, definitely dig deeper. If the canned recommendation is, due to this single number, you need to eat less, exercise more, and lose weight, but you’re already exercising 5 hours a week, your BMI or other info doesn’t indicate a need for weight loss, then take those precise recommendations with a grain of salt; think critically; dig deeper.

I also agree that, at the same time, be wary of delusion – it’s very common to think “I’m different” or “that doesn’t apply to me.” If you find yourself thinking this, confirm that you’re not engaging in self-delusion.

Where I think we might part ways is the question: Is it healthy to have A1c numbers in the prediabetic range, so long as someone exercises more than 300 minutes a week and has an acceptable body fat percentage?

I honestly don’t know the answer to that question. But I’m skeptical that the answer to that question is: “Yes, it’s healthy, and if this happens to you, the best thing to do is continue without addressing it.” (I'm not saying that you are saying this - just an overall comment.)

I’m skeptical for a few reasons. First, self-described endurance athletes, including myself, likely overestimate the impacts their training has on their physiology. In know from my experience, I have historically—and continue to!—eat too many carbs and too much fat even when running between 5 and 12 hours per week. I know this because my body comp changes, my body fat % increases even though, in my head, I’m training so much that this could not possibly be happening. And I'm hungry all the time, so how could I be over-consuming calories when it feels like I'm in a calorie deficit? But it's happening.

Second, I'm skeptical that conclusions based on “endurance athletes” should be expanded to hobbyists. This addresses your question 5. I don’t know what the threshold is, or if there’s a precise number threshold. (Probably not.)

I do know that actual endurance athletes have different lifestyles than hobbyists. For example, my brother and sister ran track and cross country and D1 schools. They ran between 70 and 100 miles a week. The duration and intensity of those miles was carefully planned and monitored. The intensity of the workouts was very high. Like, 18 miles at sub-6-minute-pace high for the weekly long run and mile repeats at 4:30-minute-pace for speed work. I don’t know precisely how many hours they spent actually running. But alongside the running they did strength training; physical therapy work; extensive warm-ups and cool-downs for each run; conscious recovery; and other ancillary work. Their meals were planned with a nutritionist. They (mostly) never gorged on crappy food. They had periodic body-composition tests. If they weren’t hitting expected times--and expected times were calculated within minutes or seconds-- they’d consult with the coach, nutritionist, sports psychologist, etc. to figure out why. It’s very possible that they would have physiological markers that differed from the general population. Any conclusions derived from this legitimate endurance-athlete population just don't translate to me, even if I’m out there running (or, more accurately, jogging/walking) 5 to 12 hours a week.

For good measure, it’s also not entirely clear to me that markers derived from a legitimate endurance-athlete population are actually “healthy” for a 41-year-old hobby-jogger. The endurance-athlete population almost surely doesn’t have metabolic disease. At the same time, it’s not clear to me that their markers would be good indicators of general health. Seems like a highly stressed population: the goal is not overall health, but instead to apply as much stress as possible without suffering a breakdown. And breakdowns/injuries were very common.

Third, it’s my understanding that the data in this area is so sparse that it’s hard to draw actual conclusions from large-scale, peer-reviewed studies.

Again, I’m not an expert, and I do not know specific answers to questions 1-3. If Kyle weighs in, all ears!

Hopefully this clarifies where I'm coming from rather than derailing.

Man. What a great well thought out post

 

[omicron1792]

Truly elite athletes (such as olympians) outlive non-elite peers. There are all kinds of confounders in there, but it pretty reliability puts to bed the idea that a lot of training is unhealthy long term.

This is based on a couple of recent survey studies of Olympic athletes and didn’t look at other factors like socioeconomic.

Not sure it exactly put the baby to bed.