Impaired glycemic response, when bad enough, is a cause of diabetes.
Insulin is not a bad thing, high blood glucose is.
When there is no need to immediately use glucose as a fuel (like when exercising), insulin is secreted. It acts as a signal to the rest of the body to remove glucose from the bloodstream and store it (as glycogen or fat). Without insulin (and without exercise), blood glucose levels would be too high for a long time.
Insulin is not a bad thing, high blood glucose is.
When there is no need to immediately use glucose as a fuel (like when exercising), insulin is secreted. It acts as a signal to the rest of the body to remove glucose from the bloodstream and store it (as glycogen or fat). Without insulin (and without exercise), blood glucose levels would be too high for a long time.