The problem with all these sorts of theories is that they do an okay job explaining the latitudinal data–we’re fat, we’re subsidizing roads, we’re subsidizing corn, so that must be making us fat!–but they don’t explain the trend. I have not done an exhaustive survey, but I’ve been unable to find any study that even attempts to establish in any sort of rigorous way that Americans have become more sedentary in, say, the last twenty or thirty years.
The data is even less persuasive for other candidates. Corn, and simple starches more broadly, have been the cheapest part of the American diet for centuries. As a child, my mother didn’t get any fresh vegetables at all eight months out of the year, because they simply weren’t available. She got frozen or canned, but their two winter staples were sugared homemade applesauce and butternut sqaush, both of which are basically pure simple carbohydrate. Lean chicken was pricier than beef, but fatty pork was cheaper than either. Look in a cookbook from the thirties or fifties and you’ll find that recipes for some sort of mostly starch dish are at least 65% of the book. And those weren’t healthy whole grains, either. They were white flour, or rice, richly laced with fat and sugar.
With the possible exception of corn subsidies (I don’t have good data on the relative penetration of corn into the food supply chain), almost every alleged deficit that is “causing” our obesity epidemic, from highways to bad urban grocery stores, is either basically the same as it was fifteen years ago, or somewhat better. So I find them deeply unsatisfying as a causal explanation for the sudden uptick in overweight people now.
To me, government behavior is at best an incredibly incomplete explanation of what’s happening. A better fit is simply that food–all food–has gotten much cheaper. People spend less of their income on food than they did thirty years ago, despite consuming a lot more of it. Stopping them from doing so will require a great deal more than subsidizing tomatoes.
Read it all.