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Questions I am Pondering!

S

Sweet Cycologist

Member
I’m trying to avoid a diabetes type 2 diagnosis for as long as possible through nutrition and exercise but I have some questions I haven’t been able to answer through my research which I’ll post as they come up and hopefully some of you lovely people may be able to help……..
 
First question ….. I am a road cyclist and ride 3-4 times a week. I know that exercise is good for controlling diabetes risk but if the “secret” is to avoid big glucose spikes, most of my big spikes come during the exercise itself and so seems counter intuitive as it increases my average glucose reading. Any thoughts or words of wisdom?
 
Sweet Cycologist said:
First question ….. I am a road cyclist and ride 3-4 times a week. I know that exercise is good for controlling diabetes risk but if the “secret” is to avoid big glucose spikes, most of my big spikes come during the exercise itself and so seems counter intuitive as it increases my average glucose reading. Any thoughts or words of wisdom?
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Hi and welcome

Sorry - my experience is that exercise is not good at controlling overall blood glucose levels, and that "avoiding big glucose spikes" is not the "secret". My view is that reducing carb intake was what lowered my BG (exercise played zero role in it, because I didn't do any) and I will still have large but reasonably short-lived BG increases with even small amounts of carb - eg 5.2 to 9.6 after a small latte, down to not all that much lactose in the milk. Back to 5.2 ish at +2hrs, so I can cope with it, but the rises are natural and expected.

I had a large and unpleasant set of diabetic symptoms beginning when my BG (measured via HbA1c) was around 43/44. Others don't get any symptoms despite much higher levels. I think it follows that we all have a tolerance level of elevated blood glucose - mine is very low. From my point of view the thing that causes damage is elevated blood glucose over time.

If you have a Google and look for CGM graphs there are plenty around from T1s, T2s and non-diabetics. The thing to bear in mind is that non-diabetic people have sharp rises and falls in blood glucose relating to food, stress/adrenaline, etc. You should expect to see rises in blood glucose if you eat carbs, or your adrenalin rises, just as you'd expect to see changes in blood pressure and heart rate with exercise.

I notice when I do strenuous exercise (for me, anything that provokes adrenalin) that my liver responds by dumping glucose for fuel. This lasts about as long as the strenuous bit lasts, and is generally gone within minutes after stopping. The glucose is synthesized by the liver, and doesn't come (directly) from food.

It's possible perhaps that you're focussing overmuch on cycling - what is happening to your BG when you eat?
 
Interesting thank you! I guess it’s a given than controlling the quality of what you eat plays a big part and I’ve learned a lot about that. It’s a normal function of the body that you will produce more glucose in your blood when you eat or exercise - that is what is supposed to happen? With all the current hype and marketing around glucose control, while educational, there is a danger that we forget that we are not supposed to have a flat line.

Because of endurance nature of the riding I do, I have to take in regular carbs to sustain the ride but I assume that the food intake goes straight into the blood stream as glucose and is used as my body’s first source of fuel before drawing from stored energy in my muscles so as long as I use it, it won’t rush to my liver to be stored for another day?

To answer you question - the response to exercise is much the same as the response to food.
 
Sweet Cycologist said:
First question ….. I am a road cyclist and ride 3-4 times a week. I know that exercise is good for controlling diabetes risk but if the “secret” is to avoid big glucose spikes, most of my big spikes come during the exercise itself and so seems counter intuitive as it increases my average glucose reading. Any thoughts or words of wisdom?
Click to expand...
Try to cycle a bit slower,(keep adrenaline down)and try having a small fruit or do it 1h after a meal or a snack (healthy that is )that way your liver will not kick in ,when my BG is about 5.6 exercise without eating ,spikes around 9 then drops one hour later,if i do it after (can of tuna +2crackers) rises after one hour to 6.8 but when i run or cycle drops steady to a 4.8 and stays there until i have my next meal .
 
Sweet Cycologist said:
First question ….. I am a road cyclist and ride 3-4 times a week. I know that exercise is good for controlling diabetes risk but if the “secret” is to avoid big glucose spikes, most of my big spikes come during the exercise itself and so seems counter intuitive as it increases my average glucose reading. Any thoughts or words of wisdom?
Click to expand...
But what does it do after the ride?

A lot of people find that whilst their glucose spikes during the intense exercise (fuelling them) for a considerable number of hours after (even a day or so) it remains lower than had they not exercised. Overall creating a better average and also maintaining and even improving insulin sensitivity. If you have any stored fat around you organs this will also be “draining” them of this excess by putting it into the blood for use.
 
Gabriel37 said:
Try to cycle a bit slower,(keep adrenaline down)and try having a small fruit or do it 1h after a meal or a snack (healthy that is )that way your liver will not kick in ,when my BG is about 5.6 exercise without eating ,spikes around 9 then drops one hour later,if i do it after (can of tuna +2crackers) rises after one hour to 6.8 but when i run or cycle drops steady to a 4.8 and stays there until i have my next meal .
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Thank you. ☺️

80% of my riding is at endurance pace - 50-75% effort of maximum effort. The rest has to be more in order to maintain and develop fitness for events. During training and events over 90 minutes I take in some carbs every 40 mins or so. Restricting carbs ended in disaster when I tried but I have become better at burning fat on my endurance rides. Going slower isn’t an option I’m afraid. I’m already spending 8-9 hours on the road.

Interestingly my ride this morning had a different response to the last time. Didn’t go as high so I’ll look at what was different.

Tbh - I’m reasonably happy with my nutrition and as I learn more I am tweaking it but I’m interested in the rationale of the science behind the accepted advice that is given around exercise. I guess it’s to do with the more holistic all round benefits which have long term health benefits. I can keep my curve very flat if I sit in the chair all day.

Thank you for the tips though. I’ll try it.
 
Are your spikes due to the carbs you are taking to fuel your rides ? If you are consuming gels or energy bars then I would assume that it them that is "spiking" the BG not the cycling. In general if you are cycling at or around zone 2 heart rate or effort then if you have a good aerobic base it is likely you will see some rise in BG over the period of cycling, however generally this wont be a spike but just a rise.
I am very experienced in endurance sport, cycling, triathlon etc, my experience of diabetes is not extensive, and I am still learning, but I have found that aerobic endurance rises blood glucose but doesn't generally spike, when you start increasing the effort then you may have a spike - this is dependant very much on how well you are fat adapted and how you initially fuelled the ride.

So IMO exercise is great for an overall reduction in BG, but depending on what you do, how hard you go and how you fuel it. Try testing less carby real foods to fuel your rides and ensure you have eaten well to fuel initially. there are several articles on the effect of endurance exercise on BG around but not loads - I feel generally that it is an area that hasnt had a huge amount of research and publication due to the historical A typical diagnosis of diabetes, not usually been athletic for type 2.
 
If you are pushing yourself to the point of collapse as you run out of glucose, I think that you are actually not getting into ketosis.
I found that I could cycle at a moderate pace for hours once I stopped using carbs as an energy source. Other symptoms were never being hungry and far less muscle fatigue after a long ride, increased strength and concentration - I go to the local university to service their knitting machines now, and it isn't difficult to pick them you and move them around but there was a time when I thought I'd have to give up the work as if the machine was on the floor it was as though it was glued there.
 
HSSS said:
But what does it do after the ride?

A lot of people find that whilst their glucose spikes during the intense exercise (fuelling them) for a considerable number of hours after (even a day or so) it remains lower than had they not exercised. Overall creating a better average and also maintaining and even improving insulin sensitivity. If you have any stored fat around you organs this will also be “draining” them of this excess by putting it into the blood for use.
Click to expand...




I’m trialling a CGM device at the moment and it’s giving me some fascinating feedback. Yesterday I did my short ride (1 hour) about an hour after my no/low carb breakfast and the during and post ride results were very different to my post porridge ride earlier in the week. A gentle curve rather than a steep peak and descent but it was mainly zone 1 with short zone 6 Intervals so I’ll keep experimenting. I’m guessing that a zone 3 ride will look different again on a different fuelling.

I should say I am not diabetic but both my parents are so I want to give myself the best chance of avoiding it for as long as possible having had a pre diabetic HBaC1 a couple of years ago. I did a lot of long distance endurance rides last year heavily relying on carbs for fuelling which worked for me but over the winter this year I wasn’t to develop my ability to use fat/protein as my main source if I can.

Thank you for your response.
 
Resurgam said:
If you are pushing yourself to the point of collapse as you run out of glucose, I think that you are actually not getting into ketosis.
I found that I could cycle at a moderate pace for hours once I stopped using carbs as an energy source. Other symptoms were never being hungry and far less muscle fatigue after a long ride, increased strength and concentration - I go to the local university to service their knitting machines now, and it isn't difficult to pick them you and move them around but there was a time when I thought I'd have to give up the work as if the machine was on the floor it was as though it was glued there.
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No collapsing - I don’t want to work that hard! I’m thinking that I could reduce my relative carb intake a little over my winter training to see what happens as the rides are much shorter. Thank you
 
If you are using a CGM, please please please take into consideration the limitations of CGMs before drawing incorrect conclusions.
For example
- insertion trauma - CGMs often report inaccurately on the first couple of days due to the "trauma" of an alien object inserted in your arm
- compression lows - CGMs will report incorrect lows if pressure is applied to a sensor. This is most common at night if you lie on your arm
- highs and lows - CGMs are designed to be most accurate at "normal" levels and may exaggerate highs and lows
- suitability - some people "suit" CGMs but other people can find them wildly inaccurate
 
In Response said:
If you are using a CGM, please please please take into consideration the limitations of CGMs before drawing incorrect conclusions.
For example
- insertion trauma - CGMs often report inaccurately on the first couple of days due to the "trauma" of an alien object inserted in your arm
- compression lows - CGMs will report incorrect lows if pressure is applied to a sensor. This is most common at night if you lie on your arm
- highs and lows - CGMs are designed to be most accurate at "normal" levels and may exaggerate highs and lows
- suitability - some people "suit" CGMs but other people can find them wildly inaccurate
Click to expand...

Hi

Thank you for your comments.

I understand the potential pitfalls but I don’t have a diabetic diagnosis so the readings are entirely to help me identify what I could consider a reasonable level of carb intake to fuel both sedentary and exercise days so it’s really only the trends I’m looking at rather than the specific values.

I have found it really useful so far but probably won’t extend beyond the free two week trial as I will get the data I need in the two weeks and it’s very expensive but I can appreciate the value and shortcomings of the system.

Thank you for your response.
 
I haven't read the entire thread yet, but as an active prediabetic cyclist (audax, touring rather than racing, hene the username!) and orienteer (racing), I have some empathy!
I spent 2 weeks in the autumn running a CGM, and during that time my highest levels (by some way) were when racing (orienteering). Not surprising really on reflection - it's the adrenaline. I'd be more worried if I didn't get such a reaction. I found that it tended to peak after 30 mins or so, and at the end of the race (around an hour or so) it would, if it hadn't already, come rapidly down to normal.
TBH, I would reckon you would want a high amount of glucose in the blood stream - how are your muscles going to get enough fuel it if isn't being transported to them? Having talked this over with a number of orienteering diabetics, high BG levels when racing are not uncommon (and the T1s I've talked to are more worried about going hypo than hyper).
I've not found gels or jelly babies (my go to when orienteering!) creating spikes during exercise - although it does seem that they help keep the level high once it is a that level.
I tried going keto, but simply couldn't make it work. It was fine for audax/touring, and could cycle 200k happily on next to no food other than some nuts, but as soon as the intensity rose (especially orienteering/running), I couldn't last more than 30-35 mins. I now follow a low carb (<100g) diet, and spot use carbs for racing days - which has transformed my performance, and has still enabled me to control my blood sugar levels. (BTW, do a fair work with sequencing food etc to keep curves under control when eating carby food - which is generally limited to pulses, some of the more carby veg - not potatoes! - and the occasional treat sourdough wholemeal bread - the one carb food I miss! I don't eat porridge etc any more sadly - it's a disaster area curve-wise even when using all the hacks to control it).
 
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Hi. Exercise can cause BS to rise or fall depending on the type of exercise. I would try to avoid eating too many carbs when countering low BS when exercising i.e. only have a many as really needed. You may be able to train the body to convert glucose stored in the liver where possible rather then relying on glucose drinks. Marathon runners do this to avoid 'hitting the wall'. When not exercising obviously keep the carbs sensibly down.
 
velofan said:
I haven't read the entire thread yet, but as an active prediabetic cyclist (audax, touring rather than racing, hene the username!) and orienteer (racing), I have some empathy!
I spent 2 weeks in the autumn running a CGM, and during that time my highest levels (by some way) were when racing (orienteering). Not surprising really on reflection - it's the adrenaline. I'd be more worried if I didn't get such a reaction. I found that it tended to peak after 30 mins or so, and at the end of the race (around an hour or so) it would, if it hadn't already, come rapidly down to normal.
TBH, I would reckon you would want a high amount of glucose in the blood stream - how are your muscles going to get enough fuel it if isn't being transported to them? Having talked this over with a number of orienteering diabetics, high BG levels when racing are not uncommon (and the T1s I've talked to are more worried about going hypo than hyper).
I've not found gels or jelly babies (my go to when orienteering!) creating spikes during exercise - although it does seem that they help keep the level high once it is a that level.
I tried going keto, but simply couldn't make it work. It was fine for audax/touring, and could cycle 200k happily on next to no food other than some nuts, but as soon as the intensity rose (especially orienteering/running), I couldn't last more than 30-35 mins. I now follow a low carb (QUOTE]

Thank you for taking the trouble to respond. Your experience matches mine and that is reassuring.

If I keep my ride low intensity then there is very little impact in BS but as soon as I increase intensity into zone 3 and above for any significant amount of time it shoots up but logically that’s what it surely should be doing!

I’m aiming to reduce my carb intake on a “normal” day from 130g to 100g which I’m managing reasonably well and yesterday I did a low intensity 50 mile ride on my normal ride day porridge breakfast and a croissant at the coffee stop and surprisingly had no issues with completing the ride comfortably so I’ve come to the conclusion that I probably don’t need as many carbs to fuel a ride as I think I do and by doing more lower carb, low intensity rides my body will adapt.

That said, if I’m doing a hard ride for more than an hour I don’t restrict carbs - that seems madness but next I’m going to try introducing more protein on longer rides to see how that impacts.

I’ve learned from the CGM what impacts my BS the most and in two weeks my average BG has dropped significantly so I seem to be on the right path.

I’m not a racer and I want to increase my distance riding so hoping my new found knowledge will help me achieve that.

Thank you for your contribution.
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Daibell said:
Hi. Exercise can cause BS to rise or fall depending on the type of exercise. I would try to avoid eating too many carbs when countering low BS when exercising i.e. only have a many as really needed. You may be able to train the body to convert glucose stored in the liver where possible rather then relying on glucose drinks. Marathon runners do this to avoid 'hitting the wall'. When not exercising obviously keep the carbs sensibly down.
Click to expand...

Thank you. I think you’ve hit the nail on the head. I’ve probably been over fuelling with carbs and am now experimenting with less carbs and more protein to fuel my rides, especially the low intensity ones. After all, I guess as long as I take in calories, my body will use them! Will see what happens.
 
This is worth a read if you have the time to wade through it:

www.ncbi.nlm.nih.gov

Skeletal Muscle Insulin Resistance: Roles of Fatty Acid Metabolism and Exercise

The purpose of this review is to provide information about the role of exercise in the prevention of skeletal muscle insulin resistance, that is, the inability of insulin to properly cause glucose uptake into skeletal muscle. Insulin resistance is associated ...
www.ncbi.nlm.nih.gov www.ncbi.nlm.nih.gov

Beyond the immediate effects on BG levels while engaged in exercise (which others have rightly stated may be associated with adrenaline levels and what you're eating before and during for example) it is thought that exercise has positive effects on insulin sensitivity in muscle tissue lasting for a considerable period of time.

"However, it had been shown earlier that at 12 hours after glycogen-depleting exercise, whole-body insulin-stimulated glucose disposal was increased slightly (compared with the resting control condition).140 Similarly, insulin sensitivity (determined by using the concentration of insulin to obtain half of the maximal whole-body insulin-stimulated glucose disposal rate) was improved immediately after 60 minutes of cycling exercise in untrained men and remained elevated for 48 hours.142"

In short, exercise makes your insulin work better at dumping blood glucose into muscle tissue for a considerable period of time after the exercise is over.
 
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