Individuals of all ages with diabetes should not be limited in their activities, and should be encouraged to participate in sports and physical activities. A person with either Type 1 or Type 2 diabetes can become an elite athlete or train and compete at a high level of exercise intensity and endurance.

Exercise usually lowers blood glucose levels because the exercising muscles use more glucose as fuel and exercise makes the body more sensitive to insulin. Lowering of blood glucose levels (BGL’s) usually occurs during exercise and for some time after exercise (can be up to 12-16 hours after exercise).

Sometimes blood sugar levels may rise during exercise or just after exercise because of the effect of the body’s other hormones, such as adrenaline. Usually BGL’s will fall after exercise for reasons outlined above. If exercising with an infection or when unwell, BGL’s are likely to rise. It is recommended to avoid exercise if unwell or if BGL’s are above 14mmol/l.

Exercise will affect everyone differently. It is therefore recommended to monitor BGL’s regularly to avoid help avoid hypoglycaemia.

Woman doing her diabetes test

Guidelines for Exercise and Diabetes

Nutritional guidelines for athletes with diabetes should be no different for athletes without diabetes. The training diet should be based on high carbohydrate, low fat, low to moderate glycaemic index foods. Athletes with diabetes should learn to adjust their insulin dosage to suit their training and lifestyle, and make only minimal changes to their eating patterns.

Athletes with diabetes need to consider:

  • The type and timing of meals.
  • Insulin dosage.
  • Regular monitoring of BGL’s.
  • Athletes with diabetes should let their coaches and trainers know about their condition. Athletes are advised to train with somebody who is familiar with the detection and treatment of hypoglycaemia.

Before exercise

Short and low level exercise may require no adjustment to insulin and food intake. Prolonged or high intensity exercise will require extra carbohydrate and/or less insulin beforehand.

It is useful to measure the blood glucose level before exercise. This helps to calculate how much extra carbohydrate may be required before exercise. It is also important to measure blood glucose levels after exercise because of the possibility of delayed hypoglycaemia.

A low glycaemic, high carbohydrate meal one to three hours before the commencement of exercise is recommended. If insulin is likely to peak at the time of the event, an additional 10-15g CHO 20-30 minutes before the event should be sufficient to maintain blood glucose levels.

Many carbohydrate foods are suitable before and during exercise, but here are some popular choices:

  • Juice
  • Milk
  • Yoghurt
  • Fruit
  • Fruit bars
  • Sandwiches
  • Low fat biscuits
  • During exercise

Dietary carbohydrate eaten at about 60 minutes into a prolonged bout of exercise helps to prevent hypoglycaemia during exercise. Solid or liquid carbohydrate can be consumed during exercise, this will depend on the type of exercise and individual preference. Suitable carbohydrate foods to consume during exercise include:

  1. Sports drinks
  2. Sports bars
  3. Jam sandwiches
  4. Fruit or fruit juice
  5. Easily digested low fat muffins/cakes
  6. After exercise

Delayed hypoglycaemia is common for up to 16 hours after the completion of exercise. This is because the body continues to use glucose and the body is more sensitive to insulin post exercise. This can be prevented by regular blood glucose monitoring, extra carbohydrate and insulin adjustment.

Carbohydrate should be consumed within 30 minutes after the completion of exercise. This will help prevent hypoglycaemia and aid recovery. An amount of 1.0 – 1.5g CHO per kilogram of body weight is recommended.

Diabetes glucose monitor in front of fruit

Fluids

Adequate hydration is essential for performance. Many athletes with diabetes tend to be preoccupied with carbohydrate and forget about fluid requirements. Excessive thirst is a sign of hypoglycaemia and fluid intakes are likely to be higher if hyperglycaemia is present. Sports drinks can be useful as they provide a valuable source of carbohydrate along with meeting fluid requirements.

Case Study

Ben is an active thirteen-year old AFL player. During the winter he has football training from 4-6pm on Tuesday and Thursday evenings. He then plays a game of football on Saturday mornings from 10-11am.

Usual insulin doses:

Morning: Protaphane 12 units, Actrapid 6 units

Evening: Protaphane 7 units, Actrapid 3 units

Adjustment:

After regular monitoring and some adjustments, the following plan was worked out.

Before football training Ben eats his usual amount of afternoon tea plus an extra 30-45g CHO depending on BGL’s. He has some sports drinks half way during the training session. He eats 45g carbohydrates straight after training (juice and a sandwich). He then goes home and eats dinner straight away. Ben has reduced his evening insulin dose to Protaphane 5 units and Actrapid 1 unit. He also eats an extra 15g CHO at supper if his BGL is less than 7 mmol/l.

On Saturday mornings Ben has reduced his insulin to Protaphane 10 units, Actrapid 4 units. He eats his usual high carbohydrate breakfast and has an early morning tea at approximately 9-9.30am. Ben also has a sports drink at half time. Ben then eats a recovery snack straight after the game and is home for lunch by 1.00pm.

Key Points

  • Athletes with diabetes are able to compete in almost all sports apart from a few exceptions that pose a high risk because of hypoglycaemia.
  • All athletes need to be properly instructed on strategies to avoid and treat hypoglycaemia.
  • Exercise usually lowers blood glucose levels, but sometimes they may go up during or just after exercise.
  • Measure BGL’s before exercise and during any prolonged exercise.
  • Some people may need to adjust insulin doses before and after exercise.
  • Eat extra carbohydrate before exercise and during prolonged exercise.

References

Clinical Sports Nutrition, edited by Louise Burke and Vicki Deakin

Caring for Diabetes in Children and Adolescents, Geoff Ambler

About the Author

Sharon Rochester is a sports dietitian currently working in private practice. Sharon is a current consultant to the Queensland Academy of Sport and has a special interest in juvenile diabetes.