100% agree with this. And I think we might agree on more than a few things. My point was that at least right now, we don’t know if this is good data, bad data, or just noise. Hence why I’m interested to see some studies on these in non-diabetic athletes.
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Apologies, I read this more whataboutism, again apologies for my responding to quickly without comprehending, but I don’t think that analogy works for Supersapiends, when it comes to caloric counting, we have evidence that calories in < calories expended = weight loss, now for some people, yes that will lead to obsessive behavior. and that is part of human nature, for me the problem with Supersapiends is that we have no x < y = z, we don’t know of there is a output, we can’t control x, and trying to do so will drive a negative feedback loop, with people adjusting diet and not eating to control x (when it’s harder to control than just diet) when we aren’t sure what y is or if there is a Z, there is no up side at the moment (IMO), and chasing these things can lead to obsessive behavior with no proven gain, unlike caloric counting which will lead to weight loss (healthy or not)
Anyway, enough damage done here, time to change my dexcom
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Define “normally healthy”. Define “typical”. What constitutes a training ride wrt blood glucose? What conclusions should we draw from your n=1 study indicating one self reported bonk in 5 years?
Crux of the matter - used properly, a CGM is as useful as a power meter, HR monitor, cadence sensor, or speedometer. It provides information related to performance. If a rider uses that data appropriately, they can learn how their body responds to various inputs and types of effort and craft an informed fueling strategy.
Of course, just like the other sensors referenced, data can be used improperly as well. We have all ready posts from riders who misused their power data or HR, or assumed their cadence had to be exceptionally high or low, etc. That dodn’t mean those sensors weren’t useful tools.
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This is an excellent analogy. It is possible to use MFP for a few days, draw all sorts of wrong conclusions, and develop terrible habits or strategies. It is also entirely possible to use it as a tool to improve your nutrition and achieve desired results (It worked for me - reversed diabetes and lost 160+ lbs). My experience certainly isn’t typical, and may not be a realistic goal for anyone else. But the availability of detailed data over time was what helped me formulate strategies that worked for me.
The tool itself is neutral. What you do with it determines its value.
The only proper documented use of a CGM is for a diabetic to help control their blood sugar and insulin levels. Healthy athletes using a CGM to control fueling on training rides is just a marketing campaign of a medical device so far.
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(Speedometer? 
)
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Aside from the obvious question from How to Tame Your Dragon ("What are you going to do about it?), there’s no real mystery as to how things like carbohydrate intake, exercise, training, and their combination impact plasma glucose levels. Data from a CGM have a higher temporal resolution, but aren’t going to lead to any significant revalations.
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If you’re going to disagree with me, please do me the courtesy of citing my argument in context, What I wrote was: “Crux of the matter - used properly, a CGM is as useful as a power meter, HR monitor, cadence sensor, or speedometer. It provides information related to performance. If a rider uses that data appropriately, they can learn how their body responds to various inputs and types of effort and craft an informed fueling strategy.”
Gosh thanks for the wiki response. That might have been appropriate had my argument stopped where you stopped quoting.
Let me offer https://lucidphilosophy.com/7-cherry-picking/
You could have even followed to my caveat: “Of course, just like the other sensors referenced, data can be used improperly as well. We have all read posts from riders who misused their power data or HR, or assumed their cadence had to be exceptionally high or low, etc. That didn’t mean those sensors weren’t useful tools.”
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If you want to jump to the chase, see paragraph 1 in Potential Limitations with CGM Use in Sport:
First and foremost, theoretical caveats relate to the as yet untested hypothesis that glucose data derived from CGMs can provide information on the success of various sports nutrition strategies implemented to optimize performance outcomes. In the case of the application of CGMs to guide fueling practices, there is currently no evidence that CGM-derived data can identify glucose values that denote optimal CHO availability or differentiate optimal and suboptimal CHO intake practices. Indeed, as previously noted, rather than measuring BG, CGM devices measure interstitial glucose concentrations, which lag behind BG values and are unable to identify rates of appearance and disappearance of blood-borne substrates.
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I used a blood glucose meter (with the finger pricks and strips) on a number of occasions (did a couple full days of hourly (plus additional at meal time) and a number of ride days at morning, meals, and pre/post ride to help me identify certain foods that spike my BG and to adjust my in-ride fueling when I was having some issues as I was increasing my weekly and per-ride hours. I didn’t even need a physiologist to help me interpret the results, or my doctor to monitor my use to make sure I didn’t get addicted to data chasing. Worked great, after a couple iterations.
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Well done, so quick question do you feel that you learned information about food that spiked your blood glucose that couldn’t have been learned from looking at the GI index of that food, did you find foods with a low GI that spiked / vice verse
Not sure what you meant by increasing pre-ride hours ?
The clinical utility of glycemic index is basically nil (1, 2, 3)
Per-ride hours. As in instead of a regular ride being 60 minutes, it’s now 75 minutes.
How did this meaningfully affect your performance?
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As far as the glucose spikes, there’s significant diabetes in my family, I’m overweight and don’t eat a carb-centric diet, so I want to fuel my rides and recover without getting diabetes. So I was drastically increasing my carb intake on longer ride days, and a) had no idea what my blood sugar runs normally during the day (it’s normal when I get my annual physical, after fasting) and wanted to see what causes spikes for me, how high the spikes are (do I get outside of normal range), and if I the BG recovers as expected in a normally functioning metabolism,and I wanted to particularly look at this on the couple days I have a oatmeal, fruit, milk, sugar breakfast, powder in the bottle, gels, crap after the ride, etc.
The first time I used the meter in this process (it is a combined ketone and blood glucose meter that I had used a year before trying to see if I could do keto while riding) I came home from a pretty intense 2 hour ride, and felt awful…dizzy, like I had low blood pressure, maybe dehydrated. Checked my blood pressure, it was good. Remembered I had the meter, checked and my glucose was low 60s…well that explains that. The next weekend, I apparently overdid the carbs because it was like 165 when I got home, I also recognized that I was trying to set a PR on the last 5-miles to my house, so I knew my body was demanding glucose. That led to a couple ride days of basically wake to after dinner finger poking.
The biggest thing I found is that my blood glucose levels are very steady, and for most of the carbs I’m eating don’t take it above 120, and it recovers fairly quickly back into the 80s & 90s, just like I hoped it would. I had to run to the pharmacy, after a 3 hour ride, to pick up an Rx. BG was 80 something when I got home from the ride, but was feeling a little bleh while I was driving into town so I grabbed a coke. A little after I got home (drank the coke on the way home) and my BG was 140+, oops…make a note of that, and then watched as it recovered like it should.
I’m very familiar with the GI index. It’s a relativity scale, and it’s part of the equation. When and how much are really important to me, also, when I’m recovering from a 2400 calorie ride, and want to do another 1400+ calorie ride the next morning. That’s the biggie…riding hard multiple days.
per-ride hours…more hours per ride (sorry)
As for my performance, obviously I’m fueling more appropriately, and I’ve got a much better base fitness, and increased my hours by 50% last year, so I’m feeling great and breaking all the PRs I set at my previous peak 6 years ago. The big thing is that I struggled with this for a number of years, and a half dozen mornings and a couple Saturdays of finger pricks and keeping a log, I had it dialed in and, most importantly, felt confident that I wasn’t putting myself in a bad spot.
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It’s good that isn’t what we are talking about
Nice post, it almost deserves it’s own thread “how I used glucose monitoring to increase my hours per ride / caloric intake”
I’ve been T1 diabetic for 40 years and forget how much experience / knowledge I’ve gained in that time, I have to look at EVERY meal and guess it carbohydrate content and GI, just to be clear I don’t know glycemic index of all good, just a sort of, fruit juice will spike sugar levels quicker than a smoothie, and both slower the coke, but I can’t tell you the GI of those foods
Do you think that finger sticking was sufficient, and maybe helped not get to obsessed, just interested as a T1 changing from finger sticks to CGM I got carried away with trying to keep my BS in a range, caused me (as a T1 diabetic, but I think my experience could be transferred to non’s) more harm than good
Thanks. I didn’t intend to go that deep into what I did, but that “pulling back the curtain aspect” of seeing what is happening in my body could be very revealing to a person, similar to weighing and logging food/calories/macros for 2 weeks, and certainly has utility in that respect. It’s in the “you don’t know what you don’t know” realm. I don’t see being obsessed (and admittedly, I’m probably diet obsessed) if I had a CGM, for all the reasons listed in posts above (lag time, limited information). It would be interesting to see what happens during a ride (taking the kit to stick my finger on a bike ride is more than I care to do, though I have considered it 
), but now that I have a good feeding strategy (and hydration, too), I’m good.
Between poor feeding and insufficient hydration in the Florida summers, I’ve had some really scary 3 hour solo rides in the local National Forest. Last summer, after figuring this stuff out, I’d spontaneously add 10 miles to explore a road, because I had enough food and sodium (and fitness), no worries. I can often tell when I haven’t kept up with eating, because climbing a hill all of a sudden is a grind…so take a gel at the top and 10 minutes later a similar hill climb feels awesome to climb.
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This
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supporting this - no sense in wearing a CGM as a non diabetic healthy person.
I am a Type 1 Diabetic and would wish I would not need to follow this data and all its implications during the whole day and through the night.
My non diabetic doctors wear a CGM once in a while and not to get specofic data, but to just test how it feels like for us. They all confirm that there is no serious benefit for non diabetics, sporty or not, to wear a CGM.
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Not scientific but a friend of mine in his late 60’s decided out of the blue to do the PanCeltic ultra endurance event last year and used one very successfully to get his fuelling right after having had a number of disasters on longer rides in his training for it. He’d never done anything like that before. It came as a bit of a shock as to how much he had to eat to keep his blood sugar relatively stable.
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