Something tells me that it's not about fasting, but the quality of food. I'm originally from Ukraine, where fasting is not popular by any means and the cancer rate is 2.5 times lower than in US. I moved to New York 5 years ago, the first thing I noticed was how fake the food is. Seriously, I was like, why the hell the food in the most popular city in the world is tasteless, is it made of plastic? Anyways. Long story short. My hypothesis is that rich countries have access to a more powerful factories/hardware/etc. to produce a lot more processed food.