This excerpt originally appeared in The Atlantic on March 5, 2012.

Obesity is an expensive, sticky problem, no doubt about that. (Megan has addressed this issue many times in many forms). But Americans themselves aren't deluded on that point. The fat=bad message has been sent and received, thank you very much. Yet government interventions like menu labeling requirements, public awareness campaigns about the dangers of sugary soda, zoning regulations to limit the prevalence of fast food restaurants, programs to eliminate "food deserts" and bring supermarkets to poor neighborhoods are multiplying. They fail, writes Marlo