To counter the exercise-induced hypoglycaemia, knowledge of the fuel of choice may be very important for insulin-dependent diabetic patients (T1DM). Fuel oxidation during exercise of long duration has been studied in detail in healthy people. No similar data are, however, available in T1DM. Aim of the present study was to investigate the time course of fuel oxidation in a group of T1DM patients and a group of well-matched healthy controls. Nine patients (47±10 years, 73±15 kg, 170±9 cm) and eight healthy controls (42±12 years, 73±13 kg, 173±5 cm) performed a 3-hrs constant intensity walk at 30% of the heart rate reserve. Blood glucose and insulin levels were determined every 30 min; fuel oxidation was calculated by indirect calorimetry from VO₂ and VCO₂ data measured periodically. Both glucose and insulin levels were higher in patients than in controls (group effect, p < 0.001). Glycaemia remained constant in healthy subjects, whereas a significant fall was observed in patients (group x time effect, p < 0.001). Glucose oxidation decreased with increasing exercise duration (time effect, p < 0.001, p < 0.001) in both groups of volunteers. In spite of the higher glucose and insulin levels and of the sucrose administered to T1DM to counter the fall in glycaemia (61 ± 47 g), no difference was observed between the two groups of volunteers (group effect, p = ns).

The illustrated data will be very useful to suggest patients how to face glycemic imbalances during prolonged exercise.