Managing exercise in type 1 diabetes is challenging. In normal metabolism the body pretty much turns off your insulin production during exercise. This is because it relies on GLUT-4 receptors to take glucose into the cells to fuel the exercise. Think of GLUT-4 receptors a little like shuttle buses transporting glucose from the blood into the cells whilst the insulin service is down.
In type 1 diabetes, managing exercise becomes quite tricky. If are using subcutaneous injections it becomes quite hard to manage exercise. This is because once the insulin is injected your body cannot turn off its production like in someone without type 1 diabetes. So you end up with a double whammy of GLUT-4 plus insulin. If you are using an insulin pump it is easier. You still have the luxury of adjusting your basal insulin to a certain extent making it easier to manage exercise.
Not being able to turn off your insulin production can be quite risky for some people because it leaves them at an increased risk of hypos. I’ve seen some patients who completely avoid exercise for this very reason.
Yet, exercise is good for you. Regardless of whether you have type 1 diabetes or not. It will help reduce your disease risk and make you more sensitive to your insulin. It also helps people manage their weight. So there are many benefits.
Therefore, people with type 1 diabetes need education about how to best manage their diabetes around exercise. This video and post is covering only the basics as a lot of the information out there requires individualisation.
3 Key factors for managing exercise in type 1 diabetes
In reality this comes down to 3 factors. The first is insulin dose adjustment.
We’d usually start with adjusting your rapid insulin dose before or after the bout of exercise. The intensity and duration of exercise will dictate how much you need to reduce this by.
As a rule of thumb if you are exercising between 0-60 minutes you may find a dose reduction of 0-50% is required. If you exercise for longer than 60 minutes you may need to go over a 50% reduction. In practice this works by calculating your meals dose. Let’s say you are reducing by 50% and work out you’d usually give 6 units for a certain meal. In this instance you would take 3 units. Keep in mind the rapid insulin works for 4.5 hours. So if you aren’t exercising for 2 hours after the meal, you might expect an increase in glucose levels prior to the exercise. This won’t always happen but you can use the exercise to bring this back down quite quickly. If the elevated glucose levels make you feel you cannot exercise, adding a small additional correction prior to exercise may help reduce the peak of the glucose spike. However, keep in mind you may need to then eat some carbohydrates during the session. Alternatively, starting with a small cardio segment to bring down the glucose levels may also work.
You may need to reduce the insulin at the meal before and after exercise because the effects of exercise continues on for longer than just the exercise session.
Eat more carbohydrates
Eating more carbohydrates before, during and after exercise is also a perfectly valid strategy. Especially if the exercise is unplanned, like at work. You can’t adjust your insulin prior to exercise if you don’t know you’re going to be exercising.
Usually you will need somewhere between 20-90g of carbohydrate per hour to prevent hypo’s during exercise. You may then need a more slow acting carbohydrate food like a banana, 200ml of milk or a slice of bread to prevent later hypo’s. If you have a meal planned soon after exercise this will work too. This is during prolonged exercise. You may not need this for a half hour walk for example.
Some people do not like the idea of eating more because they are exercising to lose weight. In reality, 20-60g of carbohydrate is not a tremendous amount of calories but it could slow weight loss progress.
Therefore, a combination of exercise adjustment and planning food is likely the best approach.
Test your glucose
Everyone is different. You will have different fitness levels, exercise intensities and durations. Therefore, your glucose response will be very individual. So it’s important to test your glucose levels and collect data about how you respond.
If you are nervous about it, I would really recommend pushing for flash or continuous glucose monitoring technology to help you assess the trends. If you haven’t got these on prescription perhaps investing in one of these for a couple of weeks might just be worth it. Typically these retail at around £50 for 10 days to 2 weeks wear.
I hope that is useful and makes sense. Watch the video for further input. This is only covering the basics. More advanced strategies do exist for managing exercise but these are best discussed with hard glucose data at our disposal. In other words, the advice needs to individualised depending on the activity, frequency, intensity, duration, insulin doses and many other factors.
Let me know if you have questions.