I suspect your good fortune has more to do with the wisdom you used in picking your ancestors...
The interplay of genes and behavior is interesting. My parents and all the relatives here did not exercise much and ate whatever. Many of the relatives here (second, third, and fourth-generation Americans) are overweight and have the usual constellation of American medical problems. But back in the old country, all the direct relations are slender and have VERY long lives. So with the same genetic material, you can avoid obesity and reduce the chances of diabetes, heart disease, stroke, cancer, and other common diseases. Some of those problems may get me in the end, but I'm going to fight them off as long as possible.