Further reading: https://www.health.harvard.edu/diseases-and-conditions/the-l...
What you are referring to may be the glycemic response, which, apart from GL, also depends on the intake of fat and protein among other things. Adding fat and protein does indeed reduce the glycemic response:
"It is generally accepted that adding fat and protein to carbohydrate reduces glycemic responses by delaying gastric emptying and stimulating insulin secretion (1,2). These effects have a number of possible implications for human nutrition, such as supporting the role of high protein or high fat diets in the management of diabetes (3,4) or being a source of criticism for the application of the glycemic index to mixed meals (1,5)." https://academic.oup.com/jn/article/136/10/2506/4746688
After all, pizza is low GI if you only measure it over 2 hours.
You mean chocolate bar or any dessert.
I think you're on to something. I think the large portion of people have an addiction to certain foods.
My first inkling was when my friend, Dr. Ross, said to me, "None of my type II diabetic patients are able to control it with diet. They all need medication." (His patients are all upper-middle class, well-adjusted for the most part).
I've seen it with my dad (type II), an ex-marine (type II), a marketing executive (type II). In all cases they were eating french toast with maple syrup (the crack cocaine of type II diabetics). It was something they knew they should not be eating, and yet they were.
These are people with discipline and strength, and yet they are unable to stick to a diet. What gives? Rather than blaming them, we should ask, "Why is this so hard for them? Why can these people who can do so many things, not eat properly?"