Diabetes, Nutrition and Endurance Exercise

Why exercise matters for diabetes

For people with type 2 diabetes, regular physical activity improves insulin sensitivity, lowers blood glucose, and can help manage weight and blood pressure. It is also protective against heart disease—an important consideration for those with diabetes. It helps with stress management and has beneficial effects for mental health.

For people with type 1 diabetes (or those with type 2 diabetes on insulin), all the above benefits apply however, those who take insulin have an added challenge: managing the risk of hypoglycaemia (low blood glucose) during or after exercise. The key is finding your balance – and that starts with planning.

You can find lots of advice regarding physical activity in our NDSS factsheet here, however this article is going to specifically focus on nutrition for prolonged physical activity.

Fuelling for endurance exercise: A dietitian’s top tips.

If you're taking on an event like Run Melbourne, or any endurance activity, (aerobic or cardiovascular activity that lasts longer than 1 hour), preparation starts long before race day. Nutrition and glucose management play a critical role – not just in performance, but in safety.

Carbohydrates: your primary fuel

For any aerobic activity, your muscles rely heavily on glucose. Eating enough carbohydrate in the lead-up, and during the event, helps keep energy levels stable and reduces your risk of hypoglycaemia.

In everyday life, we often recommend low GI, high-fibre foods to support stable blood glucose levels and good health. But during extended physical activity, your body needs easily digested carbohydrate sources. This is one of the rare times where higher GI foods - like white bread, sports drinks, or glucose gels - are not only acceptable but preferred. These high GI options will quickly deliver glucose to working muscles for energy and help maintain glucose levels in the blood (preventing hypoglycaemia).

The day before endurance activity:

• Avoid high-fibre or high-fat meals the evening before, especially if you're prone to gut upset or delayed digestion.
• Choose low-fibre carbs like white rice, pasta, or potatoes with a small amount of lean protein.
• If you’re on insulin or medications that lower glucose, check with your diabetes team in advance - some people may need to reduce background or bolus insulin in the 12–24 hours before the event.

The morning of your event:

• Have a carbohydrate-rich breakfast 1.5 to 3 hours before the start. Examples include:
  - Two slices of white toast with honey or jam
  - A banana and low-fat yoghurt
  - A low-fibre cereal e.g. rice bubbles with milk and banana
• Avoid heavy fats like butter or cheese or large protein portions as they can slow down digestion and affect blood glucose unpredictably.

During the activity:

If your event lasts longer than 60 minutes, you’ll likely need to refuel along the way.
General guidelines suggest:

• 30–60g of carbohydrate per hour (depending on body size and pace)
• Start fuelling early- ideally by 30 minutes in - and continue regularly

Easy options include:

• Sports drinks or electrolyte-carb mixes
• Energy gels (check carb content - most are 20–25g each)
• White bread with honey or jam, cut into quarters
• Bananas or other soft fruits that are easy to eat on the move

Make sure to trial these in training to avoid stomach issues and refine your plan.

Post-exercise glucose drops - why they happen and how to avoid them

After prolonged exercise, especially aerobic events like running, your body remains insulin-sensitive for several hours - sometimes up to 24 hours. This means blood glucose can continue to fall even after you’ve stopped moving.

To reduce the risk:

• Monitor glucose regularly in the hours post-exercise
• Have a balanced recovery meal or snack with carbs and protein soon after finishing e.g. a wholegrain sandwich or pasta with tuna or chicken.
• If exercising in the afternoon or evening, consider a bedtime snack with slow-acting carbohydrate (e.g. milk, wholegrain toast, low-GI fruit, yoghurt)
• If relevant, speak with your healthcare team about adjusting insulin doses before and after endurance events

Move in a way that works for you

You don’t need to be an athlete to benefit. Walking, swimming, dancing, gardening - it all counts. Aim for at least 150 minutes per week of moderate activity, include strength training twice per week, and stretching daily.

If you want individualised advice for nutrition, diabetes and exercise, consider booking an appointment with our expert dietitians in the Diabetes Victoria Clinic.