The glycemic impact of the potato can vary with how it's prepared, whether it was cooked and allowed to cool, reheated, etc. Also, what matters is the impact of the meal, so it depends on what else you eat it with. But it certainly isn't a nutrient dense food no matter how you cook it.
The problem i have with the GI scale is that it goes out the window if consumed with fibre, protein and fats. This being the case the GI scale is next to useless as this scale was made on fasted people only eating 1 carb source at a time.
So what youre saying is, if i ate the same amount of protein,fat, and fiber , and the same amount of carb source being a high glycemic index food such as white bread, my insulin wouldnt spike as much as if i ate the same amount of low glycemic carbs such as brown basmati rice?
Essentially yes however i wouldn't advocate white bread as it is loaded with a lot of crap in it.
The GI index was made by feeding a fasted individual a specific carb and then measuring the glucose response. Nothing else in their system, just that one carb source after fasting.
Now add in a mixed meal of protein, fats and i would argue that fiber is a bigger factor here. This slow down the rate of digestion and insulin response.
This is not to say, just go and eat whatever. Lower GI foods are typically more nutrient dense. The only time you need to worry about GI, assuming you monitor GI is if you have not eaten anything previously that day, if that carb source is being consumed by itself.
When i guide people through weight management my key focus is sufficient protein, fats and fiber. Fiber is hugely overlooked but it is a key aspect of health and weight management.