Impact Of Energy Surplus And Exercise On The Insulin Response To Glucose

Abstract

Short-term overfeeding (3–7 days) reduces insulin sensitivity whereas short-term exercise training enhances it. Despite real-world relevance, the impact of combined overfeeding and exercise has not been evaluated in humans. PURPOSE To test the hypothesis that a single exercise bout would improve the insulin response to a glucose challenge despite a considerable energy surplus. METHODS The baseline insulin sensitivity index (C-ISI) and area under the curves (AUC) for glucose and insulin were measured during an oral glucose tolerance test in nine healthy, recreationally active subjects (6 M, 3 F, 28.3 ± 7.5 yr, 74.9 ±13.5 kg, 54.9 ± 10.4 ml kg−1. min−1) after 48h without exercise while being fed a weight maintenance diet. The tests were repeated after 3 more sedentary days in which positive energy balance of+768 ± 68 kcal.d-1 was maintained by overfeeding (OF). Finally, C-ISI and AUC were assessed the day after overfeeding by +1502 ± 133 kcal.d which was offset by exercise expenditure of 732 ± 64 kcal to maintain approximately the same energy surplus (+747 ± 74 kcal ·d−1; OF+EX). RESULTS Blood glucose response did not differ under any condition. Compared to baseline, fasting insulin increased 41 % and 47% for OF and OF+EX, respectively. Compared to baseline, C-ISI was lower (indicating less insulin sensitivity) for OF and OF+EX (6.8 ± 0.9, 4.7 ± 0.6, 5.0 ± 2.3, respectively). OF increased the insulin AUC, whereas OF+EX decreased the insulin AUC but not to baseline levels. CONCLUSION When opposed by energy surplus a single exercise bout improves the insulin response to glucose, but the magnitude of this response may be blunted.