I would just like to explain my view please coffeeday.
When we eat high glycaemic foods, the sugar load to the body is high for everyone. A 'normal' metabolism will then respond with high amounts of insulin to get this down. If this process is repeated enough times the body will be accumulating visceral fat that blocks the insulin sensors. This is insulin resistance, where higher and higher amounts of insulin are released to cope for the same glycaemic-load. This accounts for much of the individual difference in our hormonal secretion to a specific glycaemic load.
By the time someone has prediabetes, the body is having difficulty keeping blood glucose levels normal because this insulin resistance has grown to such an extent that the body can no longer cope with the amount of carbohydrate being eaten.
Full blown type 2 diabetes, as Ivor Cummins puts it, is when the wheels have come off.
So what we have is people all along this continuum, with people having insulin resistance thinking they can eat what they like until they get a symptom, such as arthritis/gout, PCOS, osteopenia/osteoporosis, heart disease, cancer, or other associated conditions. They may never get prediabetes, but if they do it is another symptom of how severe there condition has become.