Timing of exercise for BG control

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.

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.

malcysykes1 said:

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

Click to expand...

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.

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?

Click to expand...

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:

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

, 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.

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