Exercise is an excellent way to lower glucose numbers with type-2, but many people find that their numbers are actually higher after exercise or they have lows several hours later. It helps to understand why, and to prepare for the exercise before and during so that your numbers remain stable.
This is even more important when you are on a low-carb diet, because you DO need carbs to act as fuel for the exercise. The type and timing of the exercise is also important.For mild exercise like walking, carbohydrates contribute 30% to 40% of the total calories burned. As the intensity of exercise rises, the portion of total calories burned from carbohydrate also rises, reaching about 70% of total calories during strenuous aerobic exercises like running a marathon.
if you weigh 150 pounds and walk 3 miles in an hour, you’ll use 300 calories of energy or approx. 75 mg carbs. During this mild walk, around 30% of the total carbs, or about 22 carbs, will come from carbohydrates eaten. (most of the other 70% come from fat stores for this mild exercise.) These carbohydrates come from a variety of sources, but mainly from glucose stored in muscle, glucose removed from the blood, and carbs that are eaten. All of these carbs have to be replaced within a few hours of an exercise or you stand a chance of going low and possibly rebounding high again. Most of us strive for reducing glucose numbers, so muscle and blood glucose removal is a good thing, but too much of a good thing is a bad thing. This is why it’s important to not start out with your numbers too low, because between 30 – 70 % of the glucose will be burned during the exercise, depending on the length and intensity of the exercise.
Attention to carbohydrate intake is important not only for blood sugar control but also for athletic performance. “An excellent diet cannot make an average athlete great, but a poor diet can make a great athlete average.” Although fat and protein can act as fuels during exercise, endurance begins to suffer if the amounts of fat and protein are too high in the diet. This is especially seen when exercise is long or intense.
Diets low in carbohydrate rob the muscles of the glycogen stores they need for endurance and performance. For example, a trained marathon runner on a high carb diet can run for about 4 hours before exhaustion sets in. But when on a high fat, low carb diet, the same athlete will become exhausted in less than an hour and a half, long before a marathon ends.
Athletic performance faces another challenge in diabetes. Endurance suffers not only when the diet is low in carbohydrate, but also when the blood sugar goes high or low. A high or low blood sugar means that glucose delivery to muscles as fuel is impaired and thus can directly affect performance. With diabetes, both the replacement of carbohydrate consumed by exercise, and the balancing of this carbohydrate intake with glucose numbers become critical to maximum performance.
As noted, carbohydrates make up only part of the total calories used during any particular exercise. The remaining calories come mostly from fat and a lesser amount from protein. Although fat and protein calories can affect weight and insulin levels moderately in the long-run, they have little immediate effect on blood sugars compared to carbohydrates. So to offset exercise, you first want to determine how many total carbs the exercise uses, These carbohydrates needed to balance exercise are in this carb/exercise chart below, you have to adjust it to your body and needs, but it’s a good starting point:
The chart tells us how many total carbs are required, but we also need to know when to replace them. Even if the blood sugar is normal before exercise, all of these carbohydrates are not replaced before the exercise starts. As one example, during 30 minutes of moderately strenuous exercise, like running at 8 mph, about 50% of the fuel comes from carbs, roughly 40% from internal glycogen stores in leg muscles and the other 10% directly from the blood. Only the glucose obtained from the blood has to be immediately replaced by eating or by new production of glucose. Even when insulin levels are high, glycogen use during this 30 minute run rises only to 50% with another 16% coming directly from the blood.
During the first 30 to 45 minutes of exercise, local muscle glycogen stores provide about five times as much glucose as the blood, so this is important to remember if your aim is to reduce your glucose numbers. But as the same run continues beyond 30 minutes, more carb fuel comes directly from the blood. The blood glucose contribution climbs to about 40% and the insulin level quickly drops by 50% under normal circumstances during the first 2 hours of exercise. So this is the point where you want to replace some of the carbs used or stand a chance of going low and rebounding high.
However, if your glucose levels are high to begin with and you’re using exercise to reduce them, the portion coming from the blood and needing immediate replacement would again be raised. The higher your glucose, the more eating required. Excess glucose blocks release of fuel from large internal stores in muscle glycogen and in fat pads. Eating becomes critical to the supply of fuel whenever glucose levels are high. In a way this could be compared with breaking down insulin resistance. This is another reason why we tell people that not eating can cause your numbers to go even higher, because of insulin resistance. Your aim is to release the stores from the muscles and fat supplies, and strangely enough eating the right amount of carbs for your activity helps do that. I know it sounds bacward: eat carbs to reduce the numbers, but it does work that way. In other words once you break through the insulin resistance the amount of glucose used by your system accelerates to higher levels and you stand a greater chance of going low. That’s why I say carbs are not the enemy, you just have to learn when and how to use them.
In many circumstances, though, most of the carbohydrate burned during exercise will come from these internal stores. If your numbers are at an appropriate level when exercise starts , these internal glycogen stores begin releasing their stored glucose as fuel for the exercise. Then following exercise, internal glycogen stores are rebuilt over the next 3 to 36 hours. This is done through a gradual removal of sugar from the bloodstream. The longer and the more intense an exercise, the longer it takes to rebuild these glycogen stores.
Training makes a tremendous difference. Exercises in which you rarely participate are likely to require higher numbers than those that are routine. This is why it’s also important to not “carb load” all at once before the exercise but if you’re attempting a long/more strenuous routine eating a larger amount of carbs to begin with might be advisable.
It takes experimentation at first to get to just the right levels, but it’s worth it because exercise has greater benefits than just glucose control, although it is a great way to control glucose.
If you are insulin dependent the source info will supply you more information about insulin adjustments that can be made:
source: click here
Lizzy
© EMO 5/12
Knowledge is Power
When I was diagnosed, close to 11 years ago, I was told “you are diabetic”, given a prescription for some medication, and told to wait for a nurse to come in and give me an insulin shot. When I picked up the prescription I was given a 10-page booklet telling me “All About How to Mange Diabetes”, and sent on my way. That was the extent of my “education”. 
Hi Lizzy,
thanks for the info, i am now consiously making an effort to get my glucose levels under control, so i have started exercising and checking my Bg every 2hrs. i usually exercise on an empty stomach are you saying that i should eat some form of carb before i do so?
Hi Hyacinth,
Yes, it’s never a good idea to exercise on an empty stomach because exercise uses up quite a bit of glucose and you might go low and your liver step in and send your numbers high again. Test before the exercise and use the carb/exercise chart http://lizzysdlounge.com/2012/03/17/carbexercise-chart-2/
as a guide. It will give you an idea of how many carbs to consume, and according to how long and hard the exercise session is you might have to add some during as well. Also check several hours after you stop the exercise, because the effect can last for hour after and you still might go low. After you do this for a while and find out how your body works you won’t have to test as much.
Lizzy
helpful! i love reading your articles, thanks for all.
Thanks Araceli.
Lizzy
Really a great post and valuable information.
Thanks Areta.
Lizzy
Hi Lizzy
I guess my question is more about timing of exercise. An
Example of my personal experience. I broke down and
Had pizza with my sisters. 4 pieces no less. Anyway 1 hr
Later bg was 179 and I haves learned through your methods that
I peak at 1&1/2 hrs so it was going to go higher. I got scared and took
Off walking for 30 minutes at a constant rate. My Bg dropped to
98. I was elated but had to eat something shortly after. So should I
Have waited to walk till later or should I have gone right away after
Eating??
Thanks for your reply
Well Betsy any time you walk you’ll still get the lowering effect, so right then or later doesn’t matter as much depending on when you want the lowest number. One thing about pizza though is that because it’s usually high fat it peaks later than lower fat foods. So if you usually peak at 1 to 1 1/2 hours you might peak at 2 or even 3 hours with pizza or other high fat meals. That’s something to keep in mind next time. It even has a name: “The pizza effect”, although it doesn’t just apply to pizza but anything high fat.
Lizzy