Exercise spikes & post exercise eating

[Ladynijo]

I’m recently diagnosed T2, currently experimenting with Libre. Not massively fit, but like to swim and walk.

I’ve been conscious for a while that my lines up and down the pool in the morning spikes my blood glucose, which I discovered accidentally when testing with a meter. I was a bit suprised as I hadn’t realised that exercise had this effect. I usually do about 30 mins, its not what I would call intense but it raises the heart rate and makes me feel good. I’m also getting a consistent dawn liver dump which gives a spike in the morning, taking me this morning to 6.7. On days without any exercise, breakfast (even a low carb one) will send my BG up again, although to be fair, it does come down again pretty quickly and within 2 hours its down to where it was before and sometimes lower.

Question is really what should I eat post exercise? I’m conscious that the BG level is already high, it doesn’t need any more fuel on board, and sometimes my exercise spikes will leave BG high for a long time. It seems to be different to the meal spikes in that it doesn’t dissipate as quickly. Is this because the fuel is coming from the muscles themselves? I understand that muscles store sugar too, which gets released upon exercise.

Prior to diagnosis I would use my morning swim as an excuse for a full English afterwards, but I’ve had to cut out the sourdough bread bit . The rest is probably OK ish in terms of carbs/protein, although the sausages did horrible things yesterday to my BG numbers.

I don’t want to send my BG up even higher with breakfast afterwards, but it’s usually a bit too long before lunch so I need something. I’m using the free Libre to test various things on my system, but all suggestions gratefully received.

 

[KennyA]

I’m recently diagnosed T2, currently experimenting with Libre. Not massively fit, but like to swim and walk.

I’ve been conscious for a while that my lines up and down the pool in the morning spikes my blood glucose, which I discovered accidentally when testing with a meter. I was a bit suprised as I hadn’t realised that exercise had this effect. I usually do about 30 mins, its not what I would call intense but it raises the heart rate and makes me feel good. I’m also getting a consistent dawn liver dump which gives a spike in the morning, taking me this morning to 6.7. On days without any exercise, breakfast (even a low carb one) will send my BG up again, although to be fair, it does come down again pretty quickly and within 2 hours its down to where it was before and sometimes lower.

Question is really what should I eat post exercise? I’m conscious that the BG level is already high, it doesn’t need any more fuel on board, and sometimes my exercise spikes will leave BG high for a long time. It seems to be different to the meal spikes in that it doesn’t dissipate as quickly. Is this because the fuel is coming from the muscles themselves? I understand that muscles store sugar too, which gets released upon exercise.

Prior to diagnosis I would use my morning swim as an excuse for a full English afterwards, but I’ve had to cut out the sourdough bread bit . The rest is probably OK ish in terms of carbs/protein, although the sausages did horrible things yesterday to my BG numbers.

I don’t want to send my BG up even higher with breakfast afterwards, but it’s usually a bit too long before lunch so I need something. I’m using the free Libre to test various things on my system, but all suggestions gratefully received.

I get the same sort of thing. Mild exercise tends to lower my BG, strenuous exercise puts it up (in both cases, only a little). I understand this is (as with dawn phenomenon) probably because the liver dumps its store of glucose in response to the need for energy for the muscles. As I'm generally running on ketones rather than glucose this doesn't have a big impact for me.

 

[In Response]

@Ladynijo are you sure it is your swimming causing the rise?
Could it be a "Foot on the floor" effect? Our livers release glucose at the start of the day to give us energy to get moving. Some of us see the rise before we get up. This is "Dawn Phenomenon".
Others see the rise when they "put their foot on the floor".
By exercising without eating you could be tricking your body into thinking it is starving (it is still fasting) so keeps dumping glucose.
I have Type 1 so may be slightly different. But I find eating a small amount of carbs (e.g. a small Greek yogurt) will tell my body I am ok and it will stop dumping.
It is worth experimenting. You could check to see if the rise happens on a morning when you don't swim. You could try swimming at a different time of the day. You could try a small snack before getting in the pool.

 

[Ladynijo]

I get the same sort of thing. Mild exercise tends to lower my BG, strenuous exercise puts it up (in both cases, only a little). I understand this is (as with dawn phenomenon) probably because the liver dumps its store of glucose in response to the need for energy for the muscles. As I'm generally running on ketones rather than glucose this doesn't have a big impact for me.

Thanks for responding. When you say you are running on ketones, what do you mean exactly? My understanding was that the liver stores fat, which it metabolises into glucose depending on body needs, this ends up in the blood, and that it is this stored energy which is fueling the rise in blood sugars. So even if you are consuming low carb/keto food, which won’t have much plain sugar but which will have protein and fat, ultimately all of those nutrients will get used up as the basic unit of fuel ie glucose.

 

[Ladynijo]

@Ladynijo are you sure it is your swimming causing the rise?
Could it be a "Foot on the floor" effect? Our livers release glucose at the start of the day to give us energy to get moving. Some of us see the rise before we get up. This is "Dawn Phenomenon".
Others see the rise when they "put their foot on the floor".
By exercising without eating you could be tricking your body into thinking it is starving (it is still fasting) so keeps dumping glucose.
I have Type 1 so may be slightly different. But I find eating a small amount of carbs (e.g. a small Greek yogurt) will tell my body I am ok and it will stop dumping.
It is worth experimenting. You could check to see if the rise happens on a morning when you don't swim. You could try swimming at a different time of the day. You could try a small snack before getting in the pool.

You could be right, there may be an element of ‘foot on the floor’ spiking going on in the mornings particularly. I was thinking that since I’ve been a teenager I’ve always been in a tearing hurry to get going in the morning, whether for school (7am bus) or work (6.45am train), so 50 years of training my body to do that is going to take a bit of unlearning. I now work only 3 days a week so have the luxury of a lie in for the rest, assuming I chose to take it. The body of course doesn’t realise & is probably gearing up for another fight with a sabre tooth on my morning commute.

I think there is a definite dawn thing going on as well - it kicks off around 3.30am, and I sometimes wake up at that point as well. I’ve tested whilst still in bed and then gone back to sleep, and It’s clear from the Libre graph when the line turns northwards sharply, and carries on up despite me zzzzing away. BG has been quite low overnight before that point, but not so low as to trigger any alarms (ie between 4-5mmol.) The rise does happen every day without fail, although I have yet to skip breakfast whilst on the Libre to see what that does to the pattern. I used to skip breakfast quite often, but I find I need something before lunch otherwise I lose concentration.

The breakfast spike is pretty steep most days, but its difficult to tell whether this is because of the foot on the floor thing or because the levels are already high. However, it does always return to baseline around 6 within 2 hours.

This morning pre-swim on waking was 6.7, it then hit 8.7 immediately after the swim and was starting to come down before I had breakfast. Which I kept reasonably low carb - scrambled egg and ham, and some yoghurt with berries. A negligible rise from the food, then steady downward drift to 5.8 within a hour or so. It’s then been knocking around 6.4 ever since.

So not a bad outcome although I really should try swimming at a different time to see what the effects are. I really can’t eat anything before a swim in the mornings, just not hungry and I get gastric repeats, so snacking doesn’t work for me. Trouble is I actually like a morning swim, it sets me up for the day, I find it hard to get going on anything physical after about 3pm. Still in the interests of science, I will have a go this week before the Libre expires.

 

[KennyA]

Thanks for responding. When you say you are running on ketones, what do you mean exactly? My understanding was that the liver stores fat, which it metabolises into glucose depending on body needs, this ends up in the blood, and that it is this stored energy which is fueling the rise in blood sugars. So even if you are consuming low carb/keto food, which won’t have much plain sugar but which will have protein and fat, ultimately all of those nutrients will get used up as the basic unit of fuel ie glucose.

I am running on ketones because my body is mainly using ketones, rather than glucose, for fuel. The ketones are derived from metabolised body fat (not dietary fat). I'm not sure that glucose is really the basic unit of fuel - we managed for tens of thousands of years on minimal carbohydrate consumption.

I'm not a scientist and this I know is a very simplistic version. More here:

How Ketosis & Ketones Works [Learn The Full Process Of Ketosis]

Ketosis is a process that the body goes through on an everyday basis. Learn more about what ketosis & ketones are & how they work.

www.ruled.me

Digested food is handled differently depending on what it is composed of. Carbohydrate is digested to glucose and is either used by muscles for fuel (assuming your insulin etc is working effectively) or converted to bodyfat or left in the bloodstream.

If you restrict sources of glucose from carbohydrates, your liver uses two processes to fuel your cells — ketogenesis and gluconeogenesis.

Ketogenesis takes fatty acids from stored bodyfat and dietary fat and converts them into ketones. The ketones are then released into the blood to fuel cells like our brain and muscle cells. The process by which the body burns ketones for fuel is called ketosis.

Some cells always need to use glucose for energy. To meet the energy demands that can’t be met by ketones, your liver uses a process called gluconeogenesis where the liver converts non-sugar substrates like glycerol from fatty acids, amino acids from protein, and lactate from muscles into glucose.

Together, ketogenesis and gluconeogenesis create the ketones and glucose that can meet all of the body’s energy needs when carbohydrates are restricted.

 

[Ladynijo]

Thats really helpful, thank you. I’m not a scientist either, just relying on long forgotten biology lessons! So I‘m assuming then on a ketogenic diet that the BG drops because there is little or no dietary carbs going in, and the body will only make a little glucose for its essential functions via gluconeogenesis, which presumably is a bit of a faff so it doesn’t do any more than needed, particularly given it has another mechanism to produce fuel ie Ketones. And it means that any BG spike from liver dumping glucose during exercise is going to be moderated by the fact there isn’t much floating around or stored. All very neat.

 

[KennyA]

Thats really helpful, thank you. I’m not a scientist either, just relying on long forgotten biology lessons! So I‘m assuming then on a ketogenic diet that the BG drops because there is little or no dietary carbs going in, and the body will only make a little glucose for its essential functions via gluconeogenesis, which presumably is a bit of a faff so it doesn’t do any more than needed, particularly given it has another mechanism to produce fuel ie Ketones. And it means that any BG spike from liver dumping glucose during exercise is going to be moderated by the fact there isn’t much floating around or stored. All very neat.

That's pretty much it. If you're trying to put a fire out, the first thing you do is stop adding fuel. Once you deplete the liver's glycogen stores (that's what it makes the glucose from) and close off the carb supply from food, the system has to use body fat. For me that takes 2-3 days, then I'm in ketosis. I was reading Michael Eades' blog https://michaeleades.substack.com/
recently and his view is that for most of humanity's existence it was the natural state of things.