Managing blood glucose levels around exercise remains a challenge for individuals with type 1 diabetes mellitus (T1DM), particularly because of the risk of exercise-related hypoglycemia. A randomized crossover study published in Diabetologia evaluated whether the timing and fasting status of resistance exercise influence the consistency of glycemic responses.

The study enrolled 12 adults with T1DM aged 18-55 years who had glycated haemoglobin (HbA1c) below 85 mmol/mol (10.0%) and no contraindications to resistance exercise. Participants completed six identical resistance exercise sessions under laboratory supervision at the Physical Activity and Diabetes Laboratory at the University of Alberta. Each participant completed three sessions in the morning while fasted (AM-FAST) and three in the afternoon after eating (PM-FED), with sessions conducted in random order. Capillary glucose measurements were obtained before exercise, immediately after exercise, and 30 minutes after exercise. Continuous glucose monitoring data were analyzed from immediately after exercise through 24 hours of follow-up.

During exercise, within-participant standard deviation of capillary glucose change was lower during AM-FAST sessions compared with PM-FED sessions (1.0±1.1 mmol/L vs 1.5±1.0 mmol/L; p = 0.029). Capillary glucose increased during fasted morning exercise by 1.4±1.9 mmol/L, whereas glucose decreased during afternoon fed exercise by 0.9±2.3 mmol/L (p = 0.017). No difference in variability was observed during the 30-minute seated recovery period (p = 0.76).

Continuous glucose monitoring data showed that the percentage of time spent in hyperglycemia during the 6 hours after exercise was higher following AM-FAST sessions than PM-FED sessions (56.7% vs 33.0%; p = 0.003). These findings describe differences in glycemic responses to resistance exercise performed under fasted versus fed conditions in adults with T1DM.