As President Obama signs the new federal child nutrition bill, flanked by anti-childhood-obesity crusader Michelle Obama, the culture wars have devolved into a food fight – literally. Yet it is a battle in which the political lines are not easily defined.

Unsurprisingly, Sarah Palin has led the fray. In a radio talk show appearance in November, the former vice presidential candidate derided the First Lady’s “Let’s Move” initiative – “the anti-obesity thing she is on” – as practically un-American: “She cannot trust parents to make decisions for their own children, for their own families in what we should eat.” Earlier, on a visit to a private school in Pennsylvania, Palin assailed the state’s planned school nutrition guidelines that would encourage healthier snacks and fewer classroom birthday parties; she brought a batch of 200 cookies to protest “a nanny state run amok.”

What’s more, the initiatives under fire from the right rely mainly on education and persuasion. “Empowering parents and caregivers” through access to nutritional information is one of the stated principles of Michelle Obama’s program. The proposed Pennsylvania school nutrition guidelines are voluntary. Arguably, from a true limited-government perspective, even state-backed, tax-subsidized educational efforts to encourage desirable lifestyles amounts to egregious nanny-statism. Such efforts are not new: they include such conservative favorites as the promotion of abstinence and marriage.

There are several reasons behind the backlash. One is that campaigns to promote healthy behavior have a way of escalating from friendly persuasion to ham-fisted propaganda and prohibitionism. Anti-drug zealotry in schools has caused teens to get in trouble for sharing an aspirin with a friend who had a headache. It’s not completely unreasonable to ask if cookie witch-hunts are next. And some anti-obesity crusaders advocate using the power of the state in frankly coercive ways, from taxing unhealthy food to restricting its advertising.

PERSONAL CHOICE IS A FINE THING… NOT EVERY CHOICE DESERVES CELEBRATION

Those are valid concerns. Yet there are other factors, too. One is an ultra-libertarianism hostile even to non-coercive collective efforts – through education and peer pressure, for instance – to encourage or discourage certain behaviors. The libertarian opposition is reinforced by a populist one, which regards healthy food as elitist and effete, and Big Macs and sugar-laden desserts as real American fare.

A reality check is in order. Parents have the right to decide what their children eat – but let’s not pretend that many of them don’t make woefully bad decisions. One-third of American children and teenagers are overweight while nearly 20 percent are obese. One need only look around to confirm these statistics. The consequences already include a spike in early-onset diabetes. Things will get worse when fat children become fat adults. While there is some debate about whether the hazards of moderate excess weight have been exaggerated, severe obesity is indisputably associated with a host of health risks.

Personal choice is a fine thing; but not every choice deserves to be celebrated, particularly when it is more the result of ignorance, habit and lack of self-discipline (and, sometimes, metabolic disorders) than of consciously trading better health for the pleasures of gluttony and sloth.

Nobody, adult or child, should be treated cruelly because of body weight. But the answer is not to go to the other extreme and normalize, if not glamorize, obesity or the lifestyle choices that create it.

Conservatives have often argued that individual freedom must be coupled with self-restraint. Perhaps some appreciation of this old-fashioned virtue is just what’s needed in the debate over food and fat.

CATHY YOUNG writes for Real Clear Politics.