Exercise is considered to be an important part of diabetes management for people with both type 1 and type 2 diabetes. Especially in people with type 2, exercise has been shown to improve sensitivity to your body’s own insulin, potentially reducing blood glucose levels. It can also help aid in weight loss, although the glucose-lowering benefits of exercise are evident even in people who don’t lose weight.
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But assessing the benefits and risks of exercise can be more complicated for people with type 1 diabetes, who rely on outside insulin — either injected or infused by an insulin pump — to maintain healthy and stable blood glucose levels. Since exercise can rapidly burn glucose, it can lead to hypoglycemia (low blood glucose) if your carbohydrate intake and insulin doses aren’t carefully managed. And in some people, the stress of exercise can actually lead to higher blood glucose levels, as stored glucose is released from your liver.
So it’s notable that a new study shows that in people with type 1 diabetes, exercise actually increases the amount of time people spend within a healthy blood glucose range.
Days with exercise better than sedentary days
The study, published in the journal Diabetes Technology & Therapeutics, looked at the effects of exercise in people with type 1 diabetes who wore a continuous glucose monitoring (CGM) system. They were interested in not just the immediate effects of exercise on blood glucose control, but the effect of exercise on glucose levels over a 24-hour period.
The study participants were 44 people with type 1 between the ages of 15 and 68. They were randomly assigned to exercise at home by following one of three different exercise videos twice a week. One video focused on aerobic exercise, one focused on high-intensity interval training (HIIT), and one focused on resistance exercises (weight training). Participants were also supposed to continue with their regular exercise routines, in addition to the new video-based exercises.
Wearable devices tracked how closely participants followed their assigned exercise routines, and CGM systems that they wore tracked their blood glucose levels over the study period.
The researchers defined an exercise day as a 24-hour period following an exercise routine, and a sedentary day as any 24-hour period, starting at least 24 hours after an exercise routine, during which no physical activity lasting longer than 10 minutes was recorded.
After four weeks, the results of exercise on blood glucose levels were clear among study participants. Average blood glucose levels were lower on exercise days than on sedentary days, at 150 versus 166 mg/dl. The percentage of time spent between 70 and 180 mg/dl was also higher on exercise days, at 62% versus 56% of the total time.
But not surprisingly, exercise also led to a slightly higher risk of hypoglycemia. On exercise days, participants spent an average of 9.3% of the time below 70 mg/dl, compared with 7.1% of the time on sedentary days. Exercise also led to less time spent above 180 mg/dl, at 28% of the time compared with 37% on sedentary days.
Exercise and hypoglycemia precautions both important
This study demonstrates that while exercise leads to better overall blood glucose control in people with type 1 diabetes, it also slightly increases the risk of hypoglycemia — meaning that people with type 1 should still be extra vigilant about identifying and treating low blood glucose on days when they exercise.
It’s also worth noting that no significant differences in glucose levels were seen based on the type of exercise participants completed. This means that any type of physical activity — not just aerobic exercise — may be helpful for blood glucose control, but also that people should take precautions regarding hypoglycemia with any type of exercise.
For more information on the potential benefits and pitfalls of exercise, check out “Exercise Myths and Facts.”
Want to learn more about type 1 diabetes? Read “Type 1 Diabetes Questions and Answers,” “Six Type 1 Diabetes Symptoms You Need to Know” and “Living With Type 1 Diabetes: Four Tips to Get You Started.”