Did the food environment cause the obesity epidemic?

Several putative explanations of the obesity epidemic relate to the changing food environment. Individual dietary macronutrients have each been theorized to be the prime culprit for population obesity, but these explanations are unlikely. Rather, obesity probably resulted from changes in caloric quantity and quality of the food supply in concert with an industrialized food system that produced and marketed convenient, highly-processed foods from cheap agricultural inputs. Such foods often contain high amounts of salt, sugar, fat, and flavor additives and are engineered to have supernormal appetitive properties driving increased consumption. Ubiquitous access to convenient and inexpensive food also changed normative eating behavior, with more people snacking, eating in restaurants, and spending less time preparing meals at home. While such changes in the food environment provide a likely explanation of the obesity epidemic, definitive scientific demonstration is hindered by the difficulty experimentally isolating and manipulating important variables at the population level.