Food consumed prior to exercise should supply carbohydrate that can elevate or m
ID: 274735 • Letter: F
Question
Food consumed prior to exercise should supply carbohydrate that can elevate or maintain blood glucose without dramatically increasing insulin secretion. This would theoretically optimize the availabilities of both glucose and fatty acids for use by the muscles. One concern about feeding carbohydrate prior to exercise is that a rapid increase in blood glucose- and thus insulin- might cause hypoglycemia at the start of the activity. A second effect of hyperinsulinemia prior to exercise is a reduction in lipolysis. Both of these conditions may increase reliance on muscle glycogen during the exercise. For example, Foster et al. (1979) observed that consumption of glucose 30 min before a cycling bout caused a quick increase in blood glucose but a hypoglycemic effect at the start of the exercise bout. Relative to a control trial, blood glucose and fatty acid concentrations stayed depressed for the glucose trial throughout exercise. Time to exhaustion was reduced 19% by the glucose feeding compared to the water trial. The authors concluded that glucose should not be consumed shortly before an event because this practice can cause reactive hypoglycemia and suppression of fatty acid concentration in the blood.
16. Explain using your vast knowledge of biochemistry why the phenomena bolded above is observed.
Explanation / Answer
16). Hypoglycemia that occurs after consumption of the carbohydrate-rich diet is called, "reactive hypoglycemia," which is different from the hypoglycemia that occurs during fasting. The exact cause of reactive hypoglycemia is not known, but it may occur due to reduced glucagon levels, increased sensitivity of pancreas to release excessive insulin in the presence of high blood glucose, or altered sensitivity to epinephrine (released during stress conditions). A benign tumor of beta cells in the pancreas is another possible cause of reactive hypoglycemia.