The Flour Issue

I am a new scholar. I joined a month ago in order to lose 35 pounds.
After watching the stop overeating plan I have a question about the flour issue:

I come from Russia and my grandparents survived two world wars living almost only on bread and they lived way up to their 90s with very active lifestyle.
So my brain doesn’t really see flour as something we are not designed to eat or a false pleasure like Brooke says in her videos.

Can you please expand on that?