Updated: Aug 5, 2021
Many regions of wealthy countries show a huge difference in nutrition, physical activity quality. This difference shows up in the longevity of populations living a few miles apart. The data on fiber consumption is more or less missing, but we can use proxies such as fruit and vegetable consumption to approximate the scale of the problem. Let me pick California as an example.
It is a rich state that produces around 25% of US vegetables, but only 12.3% of its people meet the daily recommendation for vegetable consumption and 23.9% got less that one portion of vegetables per day in 2019 (source: Centers for Disease Control and Prevention).
In terms of physical activity 22.4% of Californians engaged in no leisure physical activity in 2019 up from 19.1% in 2011. And California is one of the better places when compared to Louisiana, Oklahoma or Maine, which are at over 30%!)
These overall numbers however hide the more dramatic differences within the state where (roughly speaking) the coast and the valley look like two different countries. The difference in longevity is around 10 years, the difference in obesity is 37%.
While root causes are complex and numerous (e.g., education, poverty, access to healthcare, crime, drug use) their impact on nutrition and physical activity can be readily seen.