If you can find a better term for it - great. I personally think the definition is simple. If it is purchased raw it is a real food. If someone else applied a process to it first it is not.
It is fully accepted that even real food is currently tainted by farming methods, but one has to start somewhere.
Your comment about insulin reduces blood glucose and therefore must be a good thing, is at the heart of the misunderstandings about insulin .
The attached print outs stratifies 122 foods by the food insulin index lowest first.
It is utterly plain from this that the higher the FII the worse the food - I doubt you would have any debate about that.
I.e. if eating foods that produced insulin was a good thing then the correct diet for a person with diabetes would be potatoes, mars bars, rice crispie, bananas and jelly beans and the NHS advice that one should eat plenty of carbohydrates with every meal and no fats would result in massive weight loss and reversal of diabetes - it doesn't. If one has ought into the general theory of LCHF even to some degree that that is precisely the reverse of that carbohydrate heavy meal.
Instead insulin makes people fatter, because insulin is a fat making hormone and the more of it you have circulating in your body, the fatter you are likely to get and the harder to lose weight. Its my personal opinion that one gets fat because one's insulin levels become too high through eating processed foods, rather than that becoming fat gives you high insulin.
The further confusion arises because at the more detailed level in ketogenic diet debates "real food" are stratified by their insulin index in that instance it is called % insulogenic - so for example in this table below - skimmed milk is shown as 58% insulinogenic and it doesn't immediately look relateble to the other table.
https://public.tableau.com/profile/christoffer.green#!/vizhome/InsulinogenicFoodData/Dashboard1
reconciling the two tables.
I have uploaded the table of foods from the mainly processed food study and stratified that by the FII index% starting a the lowest insulinoegenic - butter followed by olive oil . If you look up skimmed fat free milk you will see its score is 60% - i.e. pretty much the same as the other table.
Looking at the tables together you can see that some " real foods " i.e. those without labels still score very high in the FII , e.g. bananas at 60% and honey dew melon at 93%.
I hope that helps in understanding it