Patients with type 1 diabetes and their providers should recognize how the form and intensity of exercise affects glucose control, according to a recent consensus statement published in the Lancet Diabetes & Endocrinology.
“Regular exercise has long been known to be beneficial from a cardiometabolic perspective for people living with type 1 diabetes. It has also been known to make glucose control more difficult,” Michael C. Riddell, PhD, professor and graduate program director at the School of Kinesiology and Health Science at the Muscle Health Research Centre at York University in Toronto, Ontario, Canada, told Endocrinology Advisor in an interview.
“This recent consensus document highlights the known beneficial effects of regular exercise in type 1 diabetes and how different forms and intensities of exercise impact immediate glucose homeostasis.”
Dr Riddell and colleagues performed a PubMed search of nutrition and glycemic-based terms for studies involving patients with type 1 diabetes or insulin-dependent diabetes between January 1990 and July 2016 in which physical activity or exercise was involved. The review of the literature was divided into sections involving management of glycemia, exercise, and nutrition, as well as goals for exercise, contraindications of exercise, and tools for exercise management in patients with type 1 diabetes.
“Acute aerobic exercise [typically causes] increases in glucose disposal that cannot be matched by increased hepatic glucose production in type 1 diabetes because circulating insulin levels do not drop rapidly enough at the time of exercise,” Dr Riddell told Endocrinology Advisor. “In contrast, elevations in catecholamines and other counterregulatory hormones, and perhaps increases in muscle metabolites like lactate, promote a rise in glucose concentrations during very high intensity anaerobic sports.”
Dr Riddell said that, in response, insulin delivery during aerobic exercises should be reduced as a response to glucose levels, whereas insulin delivery after anaerobic exercises should be increased.
Nutrition-based guidelines recommended a meal before exercise that includes a minimum of 1 g of a carbohydrate per kilogram of body weight to prevent hypoglycemia in patients with both low and high insulin, whereas the researchers recommended 10 to 20 g of carbohydrates in a meal or snack in patients with low amounts of insulin in circulation and 20 g to 30 g of carbohydrates in a meal or snack in patients with high amounts of insulin in circulation if blood glucose concentrations are 5 mmol/L (<90 mg/dL).
Exercise that lasted for up to 30 minutes should be followed by 10 to 20 g of carbohydrate for patients with low amounts of insulin in circulation and 15 to 30 g in patients with high amounts of insulin in circulation to prevent hypoglycemia in patients with a blood glucose concentration of 5 mmol/L (<90 mg/dL).
Exercise lasting between 30 and 60 minutes for patients with low amounts of insulin in circulation should be followed by 10 to 15 g of carbohydrates in low- to moderate-intensity aerobic exercise settings, whereas high-intensity aerobic exercise should be followed by 10 to 20 g of carbohydrates; to prevent hypoglycemia, patients with high amounts of insulin in circulation should consume 15 to 30 g of carbohydrates every 30 minutes, according to the guidelines.
For exercise lasting between 60 and 150 minutes, patients with low amounts of insulin in circulation should consume 30 to 60 g carbohydrates per hour, and patients with high amounts of insulin in circulation should consume up to 75 g carbohydrates per hour to avoid hypoglycemia. All patients should follow sports guidelines and adjust insulin and glycemic management when engaging in exercise lasting longer than 150 minutes.
To avoid exercise-associated dysglycemia, the researchers recommended a reduction in a patient’s bolus insulin when exercising within 120 minutes of the last dose during a prolonged aerobic exercise, but it is not advised during a brief aerobic or anaerobic exercise. A basal insulin dose reduction of approximately 20% is useful for multiple daily injections if the patient exercises less than every 3 days, if there is a high frequency of prolonged endurance exercise throughout the day, or if patients are taking twice-daily insulin.
Regarding bolus insulin doses, the researchers recommended an approximately 20% decrease of nocturnal bolus insulin for multiple daily injections to reduce the likelihood of nocturnal hypoglycemia in patients performing endurance aerobic exercises in the afternoon or early evening or hypoglycemia after a brief intense aerobic or anaerobic exercise session.
They noted that patients performing endurance aerobic exercises can reduce their temporary basal rate up to 100% up to 90 minutes before exercise but recommended some basal insulin delivery “to take into account rapid acting insulin pharmacokinetics.” Patients performing brief, intense aerobic or anaerobic exercise would benefit from increasing basal rate for hyperglycemia.
Summary and Clinical Applicability
According to the guidelines, carbohydrate intake after exercise might be beneficial based on the patient’s bolus insulin strategy, but the researchers recommended watching for the warning signs of hypoglycemia before eating carbohydrates after a brief, intense aerobic or anaerobic exercise.
Several coauthor report various financial relationships with Medtronic Diabetes, Lilly, Ascensia Diabetes Care, Insulet Corporation, the Juvenile Diabetes Research Foundation, Abbott, DexCom, Nordic Infucare, Novo Nordisk, Roche, Sanofi, Animas, MSD, AstraZeneca, Sanofi-Aventis, Amgen, Boehringer Ingelheim, Carlina Technologie, Janssen, Takeda, Adocia, Becton Dickinson, Biocon, Dance Pharmaceuticals, Grünenthal, Gulf Pharmaceuticals, Johnson & Johnson, Marvel, MedImmune, Novartis, Roche Diagnostics, Senseonics, Zealand Pharma, Mylan, Abbott Diabetes Care, Lexicon, Medscape, Omada Health, and OptumRx.
Riddell MC, Gallen IW, Smart CE, et al. Exercise management in type 1 diabetes: a consensus statement [published online January 23, 2017]. Lancet Diabetes Endocrinol. doi: 10.1016/S2213-8587(17)30014-1