JAMES TARANTO: Punishment for Gluttons: Why our diets are hard to police.

The reason that gluttony is a problem–the reason people tend to crave more food than is healthy (at least in the long term) to eat–is biological. Our ancestors had no Costco or McDonald’s; conditions of food scarcity were frequent enough that natural selection favored the instinct to eat when food was available and the capacity to store nutrients as fat as a protection against lean times.

If Bruni had omitted obesity from his discussion of Costco, it would have been a paean to the glory of the free market. Not only is the average American free from worry about famine or malnutrition; he can purchase vast quantities of good food at low prices. Even an indigent American has access to plentiful food via government programs like food stamps and school lunches.

What we are describing is not a market failure or a government failure, but a massive success of both the free market and redistributionist welfare policies, thanks to which no one in America need go hungry. The problem is that the human body is not optimally designed for conditions of such plenty. If you simply follow your appetites, you’re likely to get fat. Eating healthy requires knowledge, cognitive ability and self-discipline.

Can government regulation help? Probably not much.

The people who run our governments aren’t very good at self-discipline. What suggests that they might be able to instil in others what they so thoroughly lack themselves?