Well, an actual diabetic on insulin can eat anything they want, just do more insulin.
Of course, they need to stay on top of it, though.
Obviously accidents can happen .
Was once borderline type 2, about twelve years ago.
No more after losing weight (80lbs) and diet change.
Gained some of it back, therefore my relatively recent interest in a keto diet.
Would not advocate anyone taking medical advice over the Internet, however, Ken Berry has a video on diabetics and keto that might be interesting for anyone with type 1 or type 2 and thinking about it.
Just recently lost a type 1 diabetic friend from ketoacidosis ... scary.