Psyla. Your point about the Western diet is well taken. That said, it is a privilege of modern living to live long enough to die from a heart attack, stroke, cancer, etc. Before the advent of modern medicine and public health, if you were unfortunate enough to catch pneumonia, you died (for the most part). Tuberculosis…same. Bubonic plague…same. Smallpox…same. Etc. etc.
The human body is a complex machine, and just like any complex machine, things break. When you imagine how many “moving parts” there are in the body, starting at the macromolecular level (like the heart beating), to the cellular level (like the movement of white blood cells into infected tissues), to the molecular level (like the release of neurotransmitters) to the atomic level (like the interaction of the free radical gas nitric oxide (NO) with iron containing proteins), it is a miracle that things don’t break sooner.
So, I would say the “massive increase” in those diseases is simply a reflection of the fact that people are living longer in Western cultures, due to better health and (overall) better nutrition. When you compare the average life expectancy in Europe and the US versus (say) Africa, the difference is staggering. Africans die young from infectious diseases (HIV, TB, malaria, diarrhea) while Westerners reach old age only to die from heart disease, stroke, diabetes and cancer.