planning on taking up strenuous exercise, they may need to reduce their insulin dose.
As they become physically fitter, insulin sensitivity will improve and overall insulin requirements may decrease.
This can be judged by frequent blood glucose monitoring.
People with Type 1 diabetes are unlikely to require extra carbohydrate if blood glucose levels are above 10 mmol/l at the start of exercise and if they are taking part in light or moderate activity for 20, 30 min.
During moderate activity lasting 30, 60 min, an additional 10, 20 g carbohydrate may be required.
During strenuous activity lasting 30, 60 min, an extra 30, 50 g carbohydrate may be required.
A general rule of thumb is that 10, 20 g carbohydrate should be taken every 30 min during moderate or strenuous exercise lasting more than 30 min.
T|ming of Activity It is important to consider the timing of exercise or physical activity sessions in order to reduce the risk of hypoglycaemia.
For those taking oral hypogly- caemic agents exercise should be avoided at high-risk times, e.g. immediately before the mid-day meal.
For those taking insulin, exercise should be avoided at peak action of short-acting insulin.
The risk of hypoglycaemia appears to be lowest if exercise is taken in the morning, before taking any insulin or food.
Conversely, late afternoon or early evening exercise may increase the risk of late hypoglycaemia during the night.
The adjustment of diet and insulin for exercise is facilitated if the timing of exercise from day to day is consistent.
Summary of advice for people with diabetes wishing to exercise Before exercise: . Monitor blood glucose regularly , before, during and after exercise. . Eat a low GI meal 2, 3 h before an endurance event. . Reduce insulin by 30, 50% for strenuous or endurance training. . Optimum blood glucose levels are 6, 13 mmol/l. . If blood glucose 5 6 mmol/l, take 10, 20 g fast-acting carbohydrate. . If blood glucose 4 13 mmol/l, delay exercise.
During exercise: . 20, 30 min of light/moderate activity should not require extra carbohydrate. . 30, 60 min of moderate activity may require an extra 10, 20 g high GI carbohydrate. . 30, 60 min of strenuous activity may require an extra 30, 50 g high GI carbohydrate.
30 NUTRITIONAL MANAGEMENT OF DIABETES MELLITUS
. Endurance training may require an additional 10, 20 g high GI carbo- hydrate for each 30 min of exercise. . Remember to consume adequate fluid to prevent dehydration.
After exercise: Replenish glycogen stores by consuming high GI carbohydrate-rich foods within 30, 60 min of exercise. After endurance training, e.g. marathon running, cycling, monitor blood glucose levels, replenish glycogen stores with high GI carbohydrate and adjust insulin accordingly.