RALEIGH – Here’s a classic case of unintended consequences.

In Britain, as in America and elsewhere, there has for many years now been a great deal of public concern about rising rates of overweight and obese children. Analysts have blamed a variety of factors for the problem, including the proliferation of video games (associated with sloth) and the seductiveness of fast-food advertising (associated with gluttony). Naturally, some politicians have sought to “fix” these problems with intrusive regulation, despite basic problems of causation and effectiveness.

But when it comes to the lunch fare in public schools, policymakers understandably feel even more of a mandate to intervene to improve children’s diets. In British, famed “Naked Chef” Jamie Oliver sparked a national uproar with a television campaign in which he criticized the unhealthful food often served in school cafeterias and urged officials to take corrective action. “Basically, I wanted to get rid of the junk,” Oliver said.

Schools did so. Burgers and chicken nuggets went from routine to rare on lunch menus. Fries (chips in the U.K.) were served without salt, and both ketchup bottles and saltshakers were banished from lunchrooms. Instead, schools began to serve vegetarian pizza, baked potato wedges, and something called Quorn burgers, made up in part of fungus protein.

For the children eating their fruits, vegetables, salads, and Big Quorns, the results were no doubt salutary. But there were fewer, in some cases many fewer, children eating the school-lunch fare after the change. Coming home complaining about the food, and sometimes hungry from refusing to eat it, the children returned with bag lunches full of the very food they were forbidden to purchase at school – food packed by their own dissatisfied parents.

I must say that, being a good Aristotelian, I tend to see both sides in the dispute as embracing unattractive extremes. It sounds like the prior British practice was much like the dismal cafeteria offerings I am familiar with here, in both public and private schools: too many burger, pizzas, and tater tots, not enough healthful alternatives. On the other hand, Jamie Oliver’s misguided efforts drove British schools all the way to the opposite pole. When Food Puritans start banning saltshakers and ketchup bottles, it’s time for the culinary Roger Williamses to hit the road, corn (not Quorn) fritters in hand.

There’s a tasty, lightly toasted Golden Mean here. After some experimentation on my part, the chow for the Little Conqueror and Little General has evolved into a mix of Lunchable entrees, fruits, raw vegetables, and the occasional salty snack. More importantly, I make sure they spend a lot of time outside running around in the afternoons – running off some of what they inhaled at school. It’s the sedentary lifestyle of many children, not their diet, that primarily explains their excess weight.

But that’s not really the main point here. Britain’s school-lunch case illustrates a more fundamental aspect of sound public policymaking: the simplicist tendency to ignore feedback loops. Just changing the cafeteria food was not going to change what children actually ate unless they and their parents agreed to the change. By driving some children away from school-provided lunches altogether, administrators lost rather than gained influence over their dietary choices. We can see similar, unintended consequences in many other areas, from health and welfare policy to tax and regulatory changes.

It used to be that meddlesome politicians imagined themselves to be mechanics tinkering endlessly with “overheating economies” and “communities not hitting on all cylinders.” Now, perhaps, we’ll have to fear meddlesome politicians imagining themselves to be cooks whipping up public policies like they were fungal-burger casseroles.

Policymaking is not cooking. Your ingredients may keep hopping out of the pot.

Hood is president of the John Locke Foundation.