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Factors That May Reduce Exercise-Induced Hypoglycemia

Prandial and basal insulin reduction with carbohydrate feeding can help reduce risk of lows.

One of the reasons type 1 diabetics tend to shy away from regular exercise is due to the risk of hypoglycemia, especially evening-time exercise because it is associated with severe hypoglycemia. There are recommendations for balancing glycemic control around the time of exercise; however, these recommendations, such as prandial adjustments to bolus insulin and food alignment, are short lasting. Therefore, a study was conducted to examine the impact of a combined basal-bolus insulin dose reduction and carbohydrate feeding strategy on glycemic and metabolic parameters following evening exercise in type 1 diabetes.

The study was a randomized controlled trial that analyzed 10 male patients with an average age of 27 years and an average duration of T1DM for 12 years. Subjects had an average HbA1c level of 7% and were using a basal-bolus regimen with either glargine (n=8) or detemir (n=2) long-lasting insulin. In addition, subjects were on rapid-acting insulin aspart, and have all been controlled on these regimens for at least 12 months. All subjects were placed on continuous glucose monitoring and completed two randomized study-days separated by 1 week, where either basal insulin was not changed (the 100% group) or reduced by 20% (the 80% group). Subjects provided morning FBG, ate standardized meals and received a 75% decreased rapid-acting insulin dose after the evening meal. Subjects then completed 45 minutes of running followed by consuming a low-glycemic index meal. This activity was performed 1 hour after evening meal. Subjects’ interstitial glucose levels were also monitored for 24 hours before exercise and 24 hours after exercise. Researchers analyzed blood samples taken for glucose, glucoregulatory hormones, non-esterified fatty acids, beta-hydroxybutyrate, interleukin-6, and TNF-alpha levels.

Investigators found that 6 hours after exercise, glycemic levels were comparable between both groups, with no incidences of hypoglycemia. In the group with unchanged dosages, glucose levels decreased after six hours, where nine subjects experienced nighttime hypoglycemia. On the other hand, where 80% of insulin dosages were given, no subjects experienced nighttime a hypoglycemic state (P<0.0001). Furthermore, this group spent more time at normal BG levels (P<0.001). The next day, the 80% group had more typical blood glucose levels upon waking and before exercise (P>0.05). TNF-alpha levels were found to be normal in both study groups.

Authors conclude this is the first study to display that exercise-induced hypoglycemia can be prevented without the risk of hyperglycemia. Authors claim that people with type 1 diabetes may use a combined basal-bolus insulin reduction and low-glycemic index carbohydrate feeding strategy to avoid the risk of evening time exercise-induced hypoglycemia.

Practice Pearls:

  • Clinicians should engage in conversation with type 1 diabetes patients about exercise-induced hypoglycemia, and provide education and therapy changes to improve glucose control.
  • Findings from this study suggest that reducing basal insulin dose with reduced prandial bolus insulin and low-glycemic index carbohydrate feeding offers protection from hypoglycemia during exercise without the risk of hyperglycemia.
  • Implementing the suggested regimen from the study provides protection from exercise-induced hypoglycemia 24 hours after the evening exercise activity.

Campbell, Matthew D., et al. “Insulin therapy and dietary adjustments to normalize glycemia and prevent nocturnal hypoglycemia after evening exercise in type 1 diabetes: a randomized controlled trial.” BMJ open diabetes research & care 3.1 (2015).