I've researched all of this, and the general conclusion made by scientists and researchers is that they eat smaller portions, they stress less (probably from all the cigarettes), they drink more wine than Americans, they walk more, and the food they is fresh and natural, which I have seen to be true. In the US, where I'm originally from, there seems to be more fast food restaurants than markets. If you go to a super market, you're often given the option of poor quality produce and food out of a can.
With all the propaganda about not smoking, eating extremely small portions, even by European standards, staying away from anything that tastes good, the French have been doing the opposite, whilst maintaining proper meal portions, for hundreds of years, which the US has arguably strayed from in the last 50-60 years, and living longer.
People who move to France, as well as many other European countries, have reported improved health and lifestyle.