Insulin and Glycemic Index

As mentioned, the Glycemic Index (GI) is a scale that has been developed to measure the ability of foods to elevate blood glucose levels. Since insulin is elevated in response to rising blood glucose levels, the glycemic index can also be an indicator of how much insulin will be released from the pancreas in response to meal ingestion. The higher the number on the index, the more rapid the food can elevate glucose in the bloodstream, and the more potent the potential stimulus to the pancreas to secrete insulin. Carbohydrates like dextrose, amylopectin and maltodextrin, are very high on the GI (about 100), and therefore can be a strong stimulant to the pancreas to release insulin. Sucrose has a more moderate GI of 64, with a more moderate release of insulin. Fructose has a GI of 24, galactose 22, and fats and proteins are also low on the glycemic index. Therefore, in order to keep insulin levels balanced, choosing foods lower on the glycemic index is advocated as a way of controlling the secretion of insulin. However, these principles are only relevant during non-exercising times.

What Happens During Exercise?

It is well established that different sets of rules operate during exercise, where secretion of catabolic/counter regulatory hormones is high, and secretion of insulin is low. In fact, the more strenuous the exercise, the lower the levels of insulin, regardless of the types of food and drink you may be ingesting. This balance of hormones helps ensure that a steady supply of glucose and free fatty acids are available to provide energy to muscle cells, and helps explain why hypoglycemia secondary to insulin release is not observed during exercise.