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Sports nutrition and Type 1 diabetes

Why is regular exercise good for diabetes?

Exercise can have a positive impact on your diabetes management, as well as your general wellbeing. Here are just a few of the benefits of doing regular exercise:

  • Helps to lower blood pressure and bad cholesterol.
  • Exercise can have a positive effect on your mood.
  • It can help you relieve stress.
  • Exercise can improve your sleep.

When we're looking at diabetes management, one of the most important benefits of exercise is that it increases insulin sensitivity.

This means you'll need less insulin for the same amount of carbohydrate, and it can also help bring down post-meal blood sugar spikes. You might be able to see this effect after about 1 or 2 days after you've exercised. So, regular aerobic activity is really important when you're managing your type 1 diabetes.

It can sometimes feel like a mental workout before you’ve even started exercising because you have to decide if and how much you need to eat before and during exercise. You also need to think about what to do with insulin before, during and after exercise.

The challenges of exercising and managing type 1 diabetes

  • The risk of hypoglycaemia is high

    When someone doesn't have type 1 diabetes, their body reduces the amount of insulin they produce when they exercise. If you have type 1 diabetes, you don't produce your own insulin, so if you don't adjust the amount you take, your body will have the same amount of insulin in it when your exercise. This means that your muscles use more glucose which can cause a hypo.
  • Competitive sports can cause your blood sugar levels to increase.

    Your blood sugar, or blood glucose levels, are affected by different hormones. When you compete in exercises, like a football match, this can cause you to become nervous and stressed. Stress releases a hormone that affects your blood sugar levels making them harder to control.
  • Different types of exercise have different effects on your blood sugar.

    There are three different types of exercise that can affect your blood sugar levels.
  1. Anaerobic exercise is high-intensity exercise over a short amount of time.
  2. Aerobic exercise is lower-intensity exercise that you do over a longer amount of time.
  3. 'Stop, start' is when you do aerobic exercise broken up by short spurts of high-intensity exercise.

What are the challenges?

Exercising when you have 'insulin on board' (IOB) – for example, when you exercise soon after a meal and still have some rapid insulin in your system – may result in a greater risk of hypoglycaemia and a greater need for carbohydrate to offset the IOB. This variable means that doing the same exercise, but at different times, can result in varying effects on blood glucose. It’s essential to know how much IOB you have at the start of exercise.

Studies show that there is a large variation in how subjects respond to exercise. What this means is that guidelines are very useful, as well as learning from others, but remember that you’re an individual and your body may respond differently to another.

Learn how different types of sports or training sessions affect your blood glucose by testing before, during and after exercise, keeping a detailed record to refer back to. Remember, you're an individual so don't be alarmed if your blood glucose level behaves differently to what you expected.

Exercise and hypos

If you're worried about having hypos when you exercise, you might end up with high blood sugar levels as a result. We've created a table that you can use as a guideline before and during exercise so you can get the most out of your workout.

Starting blood sugar levels 

(note: a rule of thumb)

Less then 5mmol/L
  • Ingest 10-20g of glucose before exercise
  • Delay exercise until blood glucose is above 5mmol/L
5–8 mmol/L
  • Ingest 10g of glucose before exercise
  • Exercise can be started
  • Low-intensity exercise can be started
Greater than 15mmol/L
  • Check blood ketones
  • If no ketones, perform low-intensity exercise and/or give small correction dose of insulin
  • If ketones less than 1.0mmol/L, consider small correction dose of insulin and perform low-intensity exercise and monitor blood glucose
  • If ketones between 1–1.4mmol/L, take correction dose and exercise after 1 hour and monitor blood glucose
  • If blood ketones above 1.5mmol/L, follow regular guidance received from diabetes team for treating ketones

Research has shown that you need to be in the range of 5–8 mmol/L to increase performance during exercise. If you go low during exercise it will affect your body which is an understandable worry. But exercising with high blood sugar levels will also affect your body and lead to issues like dehydration, tiredness, and reduce your agility.

A single blood sugar test doesn't help you figure out if your blood sugar levels are going up or down. It's important before you exercise you take two tests closely together so you know if your blood sugar levels are going up or down.

Exercising with your levels in the suggested ranges will allow your body to burn more fat during exercise/ But be aware that if exercising with high blood sugar levels, you need to drink more and keep hydrated.

Fuelling for exercise


Insulin on Board or IOB is the calculation that tells you how much insulin is still active in your body. If you have low amounts of active insulin at the start of exercise, it has some benefits that include being able to use more of your fat stores during exercise, less risk of a hypo and less carbohydrate needed during exercise to maintain your blood sugar levels.

When you're preparing for a training session, try to aim to have little IOB during exercise, especially if you’re concerned about going low. This means giving thought to the timing of meals and insulin boluses and also giving thought to pre-exercise meals.

All pumps will display your IOB which is only reflecting the bolus insulin and not the basal rate or long-acting insulin.

If you take multiple daily injections, use an app which tracks active insulin or glucometers with bolus calculators.

Meal timings

Eating three hours before a training session

The action of most rapid-acting insulins is 3 to 4 hours, which means that an insulin bolus taken three hours before a training session will have little impact on the session. In this scenario, take your usual meal bolus and eat normally.

Ideally, most of the carbohydrate in the meal should be minimally processed and low glycaemic – examples of good choices include jumbo or steel-cut oats, oat and nut muesli, root vegetables such as boiled potatoes or sweet potato, whole grains such as quinoa, brown rice and bulgur wheat.

Eating two hours before a training session

Eating two hours before the session is long enough to allow you to take your usual insulin bolus, but at the same time is short enough so that you will still have some IOB at the start of the session. Reducing your meal insulin bolus at this time will likely result in higher post-meal blood sugar levels.

Consider having a low-glycaemic carbohydrate meal with a little carbohydrate. This will mean that the insulin bolus is not too large, which means less IOB during exercise. The meal should also have a small amount of fat, as too much fat at this time can mean carbohydrates take longer to absorb.

In this scenario, you will have IOB when starting exercise and so you might want to think about reducing your insulin basal rate (if using an insulin pump) at least an hour before starting exercise.

Eating 30 minutes before a training session

When you eat a meal containing carbohydrate very close to starting exercise, you can greatly reduce the carbohydrate bolus. For example, take only a quarter of your usual dose. You can also think about not taking the bolus if the basal rate isn't reduced if blood glucose is below 7mmol/L, and the exercise your doing is likely to lower your blood glucose. What you do here will be largely influenced by what your blood sugar levels are at the time.


General carbohydrate recommendations during exercise

Total IOB determines how much fuel (carbohydrate) is required before and during the session. This is in addition to other variables such as the duration and intensity of the session.

Insulin adjustments for exercise

Everyone's diabetes is different so before making any adjustments to your insulin doses, you should discuss any changes with your diabetes team.

The amount and type of insulin reduction depend on the timing, duration and intensity of the exercise.

The power of protein

While a lot of emphasis gets put on carbohydrate, protein is important for building muscle, adapting to training, recovering after training, weight loss and when recovering from an injury.

It’s worth having an idea of your protein needs and then using a calorie-tracking app for a short period to make sure you're getting enough protein to meet your fitness goals. You should try and get most of your protein from food. Although there is a place for protein powders, you should use these if it's difficult to eat food. Children and adolescents should avoid protein powders.

Weight loss

If losing weight is your long-term goal, it's important to do so in a safe, healthy way. If you'd prefer to stick to a set plan, it may be worth sitting down with your diabetes team and creating one that will work for you.

Learning Zone

Get practical advice on getting more active, from finding new activities that work for you, to exercising with your diabetes in mind, on our Learning Zone.

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