everywhere, cancer & chronic disease rates go up as diets get westernized

Yep, that's because most cancers are lifestyle related, remove alcohol, tobacco and bad diets/obesity and you remove 75% of cancers.

https://www.oatext.com/which-environment-makes-cancer.php

Obviously yes, so is most chronic disease, but bring up people being healed by lifestyle & diet intervention and prepare for relentless attacks from both doctors and laypeople.

Isn't that just selection bias, as diets get westernized so does medical care and so we detect more diseases..

this is even counter to mainstream medical opinion

Life expectancy also goes up as lives get westernized, so people live long enough to become adults and die from cancer, rather than Malaria, diarrhea, etc

rates of cancer are going up in younger people nowadays

Diet is not the only factor for cancer. There are children who die of cancer, and there are smokers and drinkers that live to 99.