David Friedman is in Europe and notes the "obesity gap" across the Atlantic. I agree. It is pretty obvious when you look around in almost any U.S. and then any European city.
Calories are cheaper than ever. Friedman also believes that the are cultural differences that matter. Keep in mind that (like it or not) U.S. culture is sooner or later widely mimiced.
Re cheaper calories, I just read Silent Spring at 50 (edited by Meiners, Desrochers and Morriss). It's a great read and I learned a bit about "The Second Agricultural Revolution" in Ch 9 of the book. I also found each of the chapters readable and enlightening.
Today's WSJ includes "For Game Day, Restaurants Throw a Party in a Box ... Clear off the coffee table: For this year's Super Bowl, some fast-food restaurants are promoting mega-meals in giant packages designed to make food the life of the party." There you have it: culture + cheap calories.