Metabolic response to different glycemic indexes of pre-exercise meal

Abstract

Introduction: To ensure performance and health, the type of food and the time of pre-exercise ingestion should be considered by practitioners of morning physical activity. Objective: This study assessed the metabolic response after pre-exercise meals with different glycemic indexes (GI) and in the fasting state adopting different types of hydration. Methods: Twelve men performed four experimental tests; two with pre-exercise meals of high GI (HGI) and low GI (LGI), and two were performed in the fasting state with hydration: water (H 2 O) and carbohydrate drink (CHO). Each test consisted of a pre-exercise rest period of 30 minutes followed by 60 minutes of cycle ergometer with continuous load equivalent to 60% of the extrapolated maximal oxygen consumption (VO 2MaxExt ). During the exercise, participants were hydrated every 15 minutes with 3mL per kg body weight. During each experimental test, venous blood samples were obtained for fasting and at 15-minute intervals during rest, and every 20 minutes during exercise. The gas analysis was carried out in periods of 5 minutes every 20 minutes of exercise. Results: There was no difference in substrate oxidation. After 20 minutes of exercise, pre-exercise food intake procedures showed similar behavior, having only reduced blood glucose levels compared to fasting procedures (p<0.01). There was maintenance of blood glucose at stable and higher levels during exercise in relation to the other tests in the fast procedure with CHO. Conclusion: The data suggest that despite the similar metabolic behavior between LGI and HGI meals, the adoption of a LGI meal before the morning exercise seems to be a more suitable feeding practice due to higher tendency of rebound hypoglycemia after HGI meal and when morning exercise is performed on fasting, hydration with CHO seems to minimize the hypoglycemic risk arising from that state.

Glycemic Index of Pre-Exercise Meal in Diabetes Mellitus: A Systematic Review

“…These results are in agreement with previous studies conducted by part our research group, however, evaluating healthy individuals. 18,19 As recommended by studies about nutritional care in glycaemic control of DM, 20,21 West et al 13 adopted an LGI meal as a pre-exercise food strategy. The sample of this study 13 was composed of individuals with type 1 DM; people in this category have a higher risk of hypoglycaemia associated with exercise, 2 which was found in the 60-min, 90-min and 120-min periods after exercise in experimental conditions.…”

Acute Cardiovascular Response to Pre-Prandial and Postprandial Exercise in Active Men

“…This phenomenon occurs as a consequence of a marked catecholamine secretion and a greater sensitivity of the adipose tissue to these hormones generated by exercise 5 . In addition, exercise in a fasting state causes an increased release of glucagon and cortisol, favoring the use of fat as energy substrate once glycogenolysis becomes restricted by the depletion of muscle and liver glycogen [6][7][8] . In this sense, the mobilization of triglycerides reserves with decreased metabolism of carbohydrates aims to preserve the glucose concentration in the blood, in order to supply the central nervous system and red blood cells 9 .…”