What is it about?

For people living with type 1 diabetes who manage their diabetes using an insulin pump, exercise can still cause low blood sugar (hypoglycemia) unless changes are made to insulin delivery. He we show that morning fasted exercise can be performed for up to at least 2 hours without the need for carbohydrate intake as long as the basal rate is lowered by 80% ninety minutes before the onset of exercise. If basal rates are not reduced, or are only reduced when the exercise starts, then some carbohydrate feeding is needed to help prevent hypoglycemia.

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Why is it important?

This work is particularly important for those people living with type 1 diabetes on pump therapy who want to exercise in a fasted state for weight loss. By turning down basal rates to 20% of the usual rate (or an 80% reduction in basal rate), then carbohydrate intake needs are minimized and ketone levels are still maintained in a safe range. This strategy also appears to increase the body's reliance on lipid as a fuel source for exercise in people living with type 1 diabetes.


For me and my colleagues on this paper who are living with type 1 diabetes, we know can see that fasted exercise can safely be performed with minimal carbohydrate intake, as long as we turn down basal insulin delivery about 90 minutes BEFORE the start of exercise. For those working in the closed loop and exercise field, we also suggest that some minimal carbohydrate intake may be needed when an insulin pump is placed in "exercise mode" or "temp target mode" just at the onset of exercise (a habit we all tend to do when the exercise no not well planned).

Michael Riddell
York University

Read the Original

This page is a summary of: Carbohydrate Requirements for Prolonged, Fasted Exercise With and Without Basal Rate Reductions in Adults With Type 1 Diabetes on Continuous Subcutaneous Insulin Infusion, Diabetes Care, December 2020, American Diabetes Association,
DOI: 10.2337/dc20-1554.
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