Or we have over-indulged in sugar and other HIGH carbohydrates and become immune to our own Insulin.
The reason insulin is less effective is that our body has lost it's sensitivity to insulin or IOW's it's ability to control insulin. Studies are showing we can get that sensitivity and control back, but not when the body has high insulin levels, either by injection or 'over-indulging in sugar'.
Without this industrial government sponsored poison in our food health would generally be much higher.