Speaking as a type 2 diabetic, I have read lots of books and articles that support what DeVany says. He has also said that many body builders are giving themselves diabetes.
Hyperinsulinemia is hypothesized to be the root cause for the epidemic of metabolic syndrome which is one or more of: obesity, diabetes, hypertension, low HDL/high triglycerides. Protein Power Lifeplan is one book that goes into some detail that is fairly understandable.
If you consider that high blood sugar precedes the insulin spike then yes, there is permanent damage. Do some searches on glycosylation. The spikes are what cause the most damage to the eyes and toes. You are cooking yourself. The damage is insidious -- it builds up in small increments over time. Of course, the less often you have your Thanksgiving meal, then the less damage. Up until my 40's, I ate foods like candy, ice cream, bread, pasta, potatoes every day.
It's hard for me at the moment to separate what damage comes from the high insulin levels vs the high blood sugar. But as I say, they are both bad and appear together. I tried to search around pubmed and elsewhere to find an article for you, but I keep getting sidetracked reading all the articles. But you can search on things like "postprandial" and "insulinemia".
I first 'met' Robb Wolf on Dr. Mikes blog about IF. I have been intrigued that IF can help regenerate red blood cells. So that is why I do it.