Timing of exercise for BG control

[Grazer]

We all know that exercise is an important part of our blood sugar control, but when is it most effective to do it, and which type of exercise?
General advice is simply to do some exercise regularly, but I had a view that if you did some serious strenuous exercise about 45 mins to an hour after your "main" meal, it would burn off some off the sugar that would otherwise remain in your blood for the two-hour post meal reading.
I do just ten minutes fairly tough work-out on a "strider" machine after the meal, and I think my two hour readings are lower each time compared to when I occassionally miss the exercise out. But how can you be sure? Is it coincidence, and would the levels have been lower/higher anyway?
Do others think this works, or is it more just about getting the daily amount of exercise in? I suppose you could argue that "x" amount of exercise uses up "y" amount of sugar regardless of when the exercise is undertaken, I just feel that more can be taken from the blood rather than the fat store if it's done when sugar levels are rising after eating.
Views would be appreciated!
Malc

 

[Snodger]

Hi Malc,
I'm type 1 so can only talk for what happens to me, but in my body, exercise does the following things:
1) uses up the sugar in my blood (if I have enough insulin sloshing around)
2) makes the insulin more effective in the short term (less insulin needed to store/use the blood sugar)
3) makes the insulin more effective in the long term (when I'm fit, I need less insulin)

Some people also find that they get a 'dump' of sugar from their liver when they exercise - the liver things 'aha, you need energy... have this'.

Everyone's different, and I don't know how well your body can use its insulin - I notice you are treated by diet alone. But I think your theory (that exercise after a meal will help with the post meal spike) is a good one.

 

[Grazer]

Thanks Snodger, makes sense what you say. Only thing is, does the potential "liver dump" you refer to mean that I'm doing the OPPOSITE to what I want - that is, the exercise uses up the sugar in the blood but therefore causes a "dump" and I end up with MORE sugar two hours after eating?!
Also, where does the sugar come from that the liver dumps? We know that sugar comes from, mainly, carbs, and is either in the blood or stored in fat tissues by insulin acting on it. So does the liver dump sugar by telling the fat tissues to release it, or does it have it's own supply from somewhere?
Or should I just stop theorizing and go and play golf?
Malc

 

[IanD]

I don't understand what's going on, but on days when I don't exercise my BG falls to around 6 before the next meal. Vigorous exercise puts it up significantly.

Today -
fasting - BG - 5.5
before tennis - BG - 7.5
after 2 sets morning tennis (only water consumed, 1½ hours, 6/7, 3/6) - BG - 8.9
Afternoon - gym 5-6 pm (gentle circuit for heart rehab group) then knocked up at badminton with my wife for 15 minutes, two youngsters were playing table tennis & one of their phones rang, so I supplanted him & we had 3 keen games 25/27, 22/24, 21/15 - BG 8.9 (nothing but water for 5 hours.)

No, I'm not giving up tennis nor t. tennis. If I measure after just the gym circuit, BG - 6 ish.

 

[Grazer]

This definitely sounds like a liver dump to me. The exercise, with no food, causes the BG to drop too low so the liver sends in an emergency supply. Recently, I had to have some tests done which required me to fast for 24 hours - O.k because I'm diet-controlled only - and I tested at the end of the 24 hours before eating, thinking "Wow, this will be a good low reading!" It was higher than normal!
I think the moral is regular amounts of low GI food rather than big gaps, particularly if you're doing a lot of exercise.
Malc

 

[Snodger]

Thanks Snodger, makes sense what you say. Only thing is, does the potential "liver dump" you refer to mean that I'm doing the OPPOSITE to what I want - that is, the exercise uses up the sugar in the blood but therefore causes a "dump" and I end up with MORE sugar two hours after eating?!
Also, where does the sugar come from that the liver dumps? We know that sugar comes from, mainly, carbs, and is either in the blood or stored in fat tissues by insulin acting on it. So does the liver dump sugar by telling the fat tissues to release it, or does it have it's own supply from somewhere?
Or should I just stop theorizing and go and play golf?
Malc

You are quite right, sugar comes from carbs that the body has broken down. Enzymes break down the carbs, the sugar sloshes about in the blood. If you have insulin and can use it, the insulin then takes that sugar in the blood, whacks some of it into the muscles that need it, and any spare it puts into the liver as storage (in storage, it's called 'glycogen'). If you are really eating lots more than you are using, the spare stored energy starts getting put into fat cells. The liver's your kind of buffer zone in a way.

So it depends on how much exercise you do. If you exercise enough to use up the sugar in your blood and no more, your liver probably won't get involved. If you exercise for longer, the liver kindly tips out a little of its stores (the 'dumping' I was referring to) to keep you going. Whether that affects your blood sugar or not will depend on how well your insulin is being used (or in my body, how much insulin I have left). A non-diabetic would just start producing an appropriate amount of insulin to balance out the sugar dump. Your body probably does as well, but if you are insulin-resistant it may not get the balance quite right.

This is why I get a bit annoyed with doctors who say exercise is unreservedly "good for diabetics". It IS good because it keeps you fit and slim and it makes insulin more effective. But it can make things more complicated, too...

I hope this hasn't made things more confusing. In your position I think a little bit of exercise after the meal is a really good idea. Golf is actually probably perfect! Test your blood and see how your body responds.

 

[Grazer]

Thanks Snodger, really good answer. The liver acting as a "buffer" is about the best description I've heard for explaining things. I'll keep up the exercise, and definitely the golf!
Malc

 

[phoenix]

We know that sugar comes from, mainly, carbs, and is either in the blood or stored in fat tissues by insulin acting on it. So does the liver dump sugar by telling the fat tissues to release it, or does it have it's own supply from somewhere?

It isn't quite like that I wrote this earlier today and saved it so some is a repeat of Snodgers post.
Actually there is very little glucose in the blood of anyone, even with out of control diabetes.
Someone with a BG of 5mmol/l actually has 0.9g of glucose in every litre of blood, even with a glucose level of say 15mmol, there is only 2.7g in every litre.
Even on the lowest carb diet you're going to take in much more glucose than that.

During the 3 hours after a meal of 100g of carb eaten by a man with a healthy metabolism, about 40g would be used and the rest stored. Glucose is coverted in the liver to glycogen which is stored there or in the muscle cells.
Muscle cells have a capacity of about 600gs of glycogen (and a trained athlete has more storage here) and the liver about 100g. It is only when the stores are full that any glucose is converted to fat. Fat is primarily stored as fat. The liver can if necessary also manufacture glycogen from proteins and fats.(gluconeogenesis, glyceroneogenesis )

When you exercise for longer than about 20min the body will need to conserve fuels. It does this by using both glucose and fat. (it is normal to use fat stores for this and doesn't require any 'switch') The proportions of each type of fuel used depends on the intensity of the exercise. On the whole steady aerobic exercise tends to utilise a higher percentage of fat, once your heart rate gets above 70% more glucose is required in the mix. If you include some flat out intense exercise, like intervals with sprints, or playing football or a game like tennis or lifting heavy weights then this anaerobic exercise will require more glucose from stores.. fat can't provide the fast energy needed.

It is insulin and glucagon working in opposition that keep the fuel supplies running smoothly. Low glucose levels causes insulin levels to fall, glucagon levels rise and glycogen (glucose) is released. Higher glucose levels result in higher insulin levels, lowers glucagon levels surpressing glycogen release. At the same time, higher insulin levels reduce the amount of fat broken down for fuel.(and the opposite)

The problem with diabetes is that the mechanisms for making a finely tuned system work efficiently are up the creek!

We either have not enough insulin or too much. Those of us that inject can't reduce the insulin immediately. Some people may have severe insulin resistance.
Some may also either over secrete glucagon (or perhaps glucagon may cause more glucose to be released than in someone with a 'normal' metabolism.) The result is that when there is a normal demand for glycogen, glucagon rises but glucose from the liver is oversupplied. (the liver dump)

Your idea of taking up golf isn't a bad one for keeping glucose levels down. It is sustained aerobic exercise, it's not likely to make your heart rate go too high and demand lots of extra glucose to fuel it.
Of course you do need to walk the course, ( using a buggy won't work :wink: ) It may be even better if you carry your bag.
There is one problem though, don't be too competitive or frustrated if you loose your ball, or it get's plugged in a bunker. Adrenalin and other 'stress' hormones also stimulate glucagon to release glucose (needed for fight or flight) so this could defeat the object :lol:

 

[IanD]

I've checked, & after a quiet afternoon, BG was 6.5 after 5 hours.

 

[Grazer]

Thanks Phoenix. Blimey, did you do a PHd in Pancreatic functions? Very helpful. Think I've got it. After my meal with carbs, my BG goes up. My Pancreas releases what Insulin it can these days to take the sugar out and store it as Glycogen in the liver. My aerobic exercise after the meal should help the efforts by the insulin by using up some of that sugar PROVIDING I don't overdo it, otherwise my sugar can go TOO low, then the Pancreas will release Glucogon which will make the liver release Glycogen to restore the deficiency. Then, my hard exercise has been counter-productive because my BG is now probably higher than it was before.
Have I got it now?
If I have, my final question is, how soon after my over-exercise would the glycogen release raise my BG? If I knew that, I could test at the appropriate time after exercise to check the state of play and modify in future to allow for this.
Malc

 

[sweetj]

, post: 212178, member: 12578"]It isn't quite like that I wrote this earlier today and saved it so some is a repeat of Snodgers post.
Actually there is very little glucose in the blood of anyone, even with out of control diabetes.
Someone with a BG of 5mmol/l actually has 0.9g of glucose in every litre of blood, even with a glucose level of say 15mmol, there is only 2.7g in every litre.
Even on the lowest carb diet you're going to take in much more glucose than that.

During the 3 hours after a meal of 100g of carb eaten by a man with a healthy metabolism, about 40g would be used and the rest stored. Glucose is coverted in the liver to glycogen which is stored there or in the muscle cells.
Muscle cells have a capacity of about 600gs of glycogen (and a trained athlete has more storage here) and the liver about 100g. It is only when the stores are full that any glucose is converted to fat. Fat is primarily stored as fat. The liver can if necessary also manufacture glycogen from proteins and fats.(gluconeogenesis, glyceroneogenesis )

When you exercise for longer than about 20min the body will need to conserve fuels. It does this by using both glucose and fat. (it is normal to use fat stores for this and doesn't require any 'switch') The proportions of each type of fuel used depends on the intensity of the exercise. On the whole steady aerobic exercise tends to utilise a higher percentage of fat, once your heart rate gets above 70% more glucose is required in the mix. If you include some flat out intense exercise, like intervals with sprints, or playing football or a game like tennis or lifting heavy weights then this anaerobic exercise will require more glucose from stores.. fat can't provide the fast energy needed.

It is insulin and glucagon working in opposition that keep the fuel supplies running smoothly. Low glucose levels causes insulin levels to fall, glucagon levels rise and glycogen (glucose) is released. Higher glucose levels result in higher insulin levels, lowers glucagon levels surpressing glycogen release. At the same time, higher insulin levels reduce the amount of fat broken down for fuel.(and the opposite)

The problem with diabetes is that the mechanisms for making a finely tuned system work efficiently are up the creek!

We either have not enough insulin or too much. Those of us that inject can't reduce the insulin immediately. Some people may have severe insulin resistance.
Some may also either over secrete glucagon (or perhaps glucagon may cause more glucose to be released than in someone with a 'normal' metabolism.) The result is that when there is a normal demand for glycogen, glucagon rises but glucose from the liver is oversupplied. (the liver dump)

Your idea of taking up golf isn't a bad one for keeping glucose levels down. It is sustained aerobic exercise, it's not likely to make your heart rate go too high and demand lots of extra glucose to fuel it.
Of course you do need to walk the course, ( using a buggy won't work :wink: ) It may be even better if you carry your bag.
There is one problem though, don't be too competitive or frustrated if you loose your ball, or it get's plugged in a bunker. Adrenalin and other 'stress' hormones also stimulate glucagon to release glucose (needed for fight or flight) so this could defeat the object :lol:[/QUOTE]

Thanks for the detailed info, its interesting to know. Could you help me with a couple of questions. I wanted to find out how long it took to restore glycogen levels after a hypo. Does it take about 3 hours? Also if I have to keep my blood sugars sugars slightly raised for this length of time, what constitutes slightly raised? Is 8 -10 about right or is this too high even for 3 hours? I'm type 1 and have been for 51 years I'm trying to regain control after a stressful period in my life. I have peripheral neuropathy and ligament problems but this doesn't impinge excessively on my life at the moment.

 

[sweetj]

What did I do to make Pheonix's explanation of glucose metabolism part of my reply? I feel like a plagiarist. Sorry.