Dr Richard Bernstein is an engineer and a doctor and also a Type 1 diabetic living on regular insulin since 7 decades. He went to medical school at the age of 45 so that he can legally practice and guide diabetics on how to really control and manage diabetes.
Check out his views on ADA diet for diabetics
He has even reversed his kidney disease on his ketogenic diet and his kidney functions like that of a 20 year old after high blood sugars caused damage to his kidneys. ADA doesn't comment on him and his opposition to ADA's diet