Whether one might live longer moving to (for example) Japan, which has the longest lifespan, has been the subject of a number of studies. Or even whether moving to France might reduce a man's risk of heart attack.
The answer seems to be clear as mud. Japanese people that live in the USA retain long lifespans. There seems to be a lot of information claiming that "diet" is responsible, but clearly good genes play a major role. An insurance company study made bold claims that the typical Japanese diet was responsible for the lifespan, by reducing circulatory issues and cancers. But the fact remains, Asian people have fewer MI's (heart attacks), strokes and cancers when compared to the average Westerner, without regard to diet, exercise or location.
I live on the East coast of South Florida, which seems to be in the USA's top tier. Will I live longer if I move to Japan? From what I can tell, the answer seems to be no.
Spooderman89,
CC BY-SA 4.0, via Wikimedia Commons
There is no question in my mind, the USA's food supply is directly causing people to become obese (a major risk factor for early death) likely from hormones, and other chemicals in our foods. Furthermore, we have very high rates of thyroid failure, a common cause of obesity. In fact, the USA is second only to China and Brazil with regard to thyroid failure. And Brazil may be directly a result of excess iodine consumption.
In any case, take an Obese American to many remote countries, feed them the exact same amount of food and watch the weight come off. We see it happen almost instantly when we travel.