Excess insulin inhibits glucagon release. Glucagon regulates blood sugar levels. Without glucagon the body uses cortisol which ages it rapidly. Insulin resistance or the inability to use insulin. When faced with resistance the body makes even more insulin in hopes of overpowering the cells.
Resistance is caused by eating too much carbohydrate and by a lack of essential nutrients.
We are not genetically programmed to eat carbohydrates and it shows in our over stimulated insulin production. The other side of the coin is excess blood sugar which causes glycosylation or glycation, a binding of sugar to proteins. Diabetics get more of this and they get it faster, but anyone who sustains elevated blood glucose will end up the same way. The end result is a decrease in glucose tolerance and increased insulin resistance. If you must eat them then do so sparingly.