"[Since] the 1950s, study after study has shown that the Mediterranean diet, and especially the diet of Crete, makes you live longer, protects you from heart disease and cancer, and keeps you from getting too fat. Look at lists of the world's healthiest diets, and the one from Crete often ranks at the top.
Unfortunately, hardly anybody follows it anymore."
See, a diet that the poor could afford in the 1950s was healthier because it was a diet of real food, mostly green stuff and olive oil in this part of the world. It's different today because now processed foods are cheaper. And thus the poor can't easily afford real food. Which is why the poor suffer higher rates of chronic disease. Of course, anybody eating a bad diet will make themselves likelier to get chronic disease, rich or poor. And because this is the case, these diseases appear to occur to a larger proportion of people than ever in human history.
Anyway, you may find the interesting story on the Cretan diet (the genesis of the Mediterranean Diet) and modern-day Cretans' health being worse to their abandoning their traditional diet insightful.