Carbohydrate Requirements for Prolonged, Fasted Exercise With and Without Basal Rate Reductions in Adults With Type 1 Diabetes on Continuous Subcutaneous Insulin Infusion
Sarah McGaugh, Dessi P. Zaharieva, Rubin Pooni, Ninoschka C. D’Souza, Todd Vienneau, Trang T. Ly, Michael C. Riddell
Abstract
OBJECTIVE Exercising while fasted with type 1 diabetes facilitates weight loss; however, the best strategy to maintain glucose stability remains unclear. RESEARCH DESIGN AND METHODS Fifteen adults on continuous subcutaneous insulin infusion completed three sessions of fasted walking (120 min at 45% VO2max) in a randomized crossover design: 50% basal rate reduction, set 90 min pre-exercise (−90min50%BRR); usual basal rate with carbohydrate intake of 0.3 g/kg/h (CHO-only); and combined 50% basal rate reduction set at exercise onset with carbohydrate intake of 0.3 g/kg/h (Combo). RESULTS Combo had a smaller change in glucose (5 ± 47 mg/dL) versus CHO-only (−49 ± 61 mg/dL, P = 0.03) or −90min50%BRR (−34 ± 45 mg/dL). The −90min50%BRR strategy produced higher β-hydroxybutyrate levels (0.4 ± 0.3 vs. 0.1 ± 0.1 mmol/L) and greater fat oxidation (0.51 ± 0.2 vs. 0.39 ± 0.1 g/min) than CHO-only (both P < 0.05). CONCLUSIONS All strategies examined produced stable glycemia for fasted exercise, but a 50% basal rate reduction, set 90 min pre-exercise, eliminates carbohydrate needs and enhances fat oxidation better than carbohydrate feeding with or without a basal rate reduction set at exercise onset.