Americans eat too much (in terms of portion size) and exercise too little. This is why we have an obesity epidemic.
That's it in a nutshell.
Personal ( empirical ) observation? I live in the deep South, and most of my older friends and relatives smoked, drank, and ate fried foods, beans cooked in bacon, eggs- all the "bad" stuff.
Most lived into their eighties, and a few into their nineties-- and they all did well until they stopped moving and working- that's when they fell apart.