Insulin is responsible for allowing sugar to enter the cell.  It is then either burned for energy or stored as fat.

In moderation, insulin is an essential and important hormone.  We would die without it.  However, due to a diet that promotes high blood sugar, our insulin is always on the rise, causing our bodies to become resistant to this hormone. Our cells become non-receptive to insulin forcing larger amounts to be produced to make up for its loss of function.

In excessive amounts, insulin has many harmful effects.  It promotes the storage of fat, especially in the abdomen and blood vessels, and blocks the function of growth hormone.  Loss of growth hormone and its inability to be absorbed into the cell is a significant cause of degeneration and aging.