1. the diet of Okinawans is irrelevant because they are not eating the refined carbohydrates that we do and
2. that fasting is easier if you eat high fat, low carbs meals just before is a fact known for thousands of years, because fasting isn't new ... all major religions that practice water fasting allow meat just before a water fast
I think you missed the point the parent was making. No one is forcing you to eat refined carbohydrates. People conflate carbohydrates with "refined carbohydrates" and end up thinking that eating a bowl of brow rice, lentils and veggies will make you diabetic because "carbs".
https://www.healthline.com/nutrition/15-incredibly-filling-f...
Legumes are high in carbohydrates and protein and are extremely nutritious and filling.
I have reactive hypoglycemia, and potatoes are something I strongly avoid for this reason (they will cause me to hypo as soon as 30 mins after eating them).
Eating potatoes causes your blood sugar to rise rapidly. When it falls, it invokes a feeling of hunger. Blood glucose can be measured directly in the blood, and isn't a matter of opinion or anecdote :P
I was suspicious of the results, so I just downloaded the paper that your link refers to - low and behold, it has this at the end:
"This study was supported by a competitive investigator-initiated grant from the US Potato Board"
Well, what a surprise!
Source: https://en.wikipedia.org/wiki/Hara_hachi_bun_me
I'm actually surprised that Wikipedia says they consume 1800 calories a day. When I am doing intermittent fasting I am around 1400-1600.