One key ingredient in Sarah Palin’s political dynamite is the cheerful scorn with which she regards Washington, a small but zesty serving of which she recently dished up for First Lady Michelle Obama and her anti-obesity crusade. During an episode of her reality show, the once (and future?) candidate cooked up a mess of hot s’mores and a side of even hotter politics, declaring: “This is in honor of Michelle Obama, who said the other day we should not have dessert.”

Palin was being over-generous in her paraphrase. What Mrs. Obama in fact said was considerably more worrisome: “We can’t just leave it up the parents.” Her particular target was unhealthful school lunches, which parents presumably require help from distant federal authorities to improve; it is clear from this and much else that the first lady envisions a very broad role for the federal government in menu planning. If her vision leaves any room for limitation on government interference in family affairs, it is impossible to detect it. Palin, responding specifically to this boundless license for federal meddling, later expanded on her views: “Instead of a government thinking that they need to take over and make decisions for us, according to some politician’s — or politician’s wife’s — priorities, just leave us alone, get off our back, and allow us, as individuals, to exercise our own God-given rights to make our own decisions.” (There is something particularly delicious in Palin’s tone when she pronounces the words “politician’s wife” — if there should be such a thing as a Palin administration, we are confident that the apparently easygoing Mr. Palin will not evolve into the first scold.)

As is the case with practically all things Palin, this latest statement has led to a predictable chorus of harrumphing nanny-staters, not every one of whom is obviously qualified to lecture the body politic on healthful eating. CNN’s fulsome Roland Martin declared Palin’s observation “so stupid that it defies logic,” and added that the former governor is too ignorant to “understand how devastating obesity is to the future of the United States.” Defying logic, Mr. Martin, along with practically all of Mrs. Palin’s critics on the issue, is missing a piece in his argument: specifically, even a smattering of evidence that busybody campaigns of the sort in which Mrs. Obama is engaged are likely to do more good than harm when it comes to extraordinarily complex issues such as obesity — which is indeed positioned to impose significant costs, both financial and human, on the American people.

The evidence is, in fact, to the contrary, suggesting that well-intentioned government policies will make the problem worse: To the extent that political action has thus far affected American obesity, it has been a thumb on the wrong side of the scales, subsidizing the worst kinds of foods through the farm-subsidy and school-lunch programs, and often giving out precisely the wrong kind of dietary advice.

Obesity is, in truth, among our least tractable public-health problems. It is an absolute Gordian knot of nutrition, behavior, genetics, child-rearing environments, hormonal biology, economics, and other factors too numerous and too subtle to catalog. As New York University obesity-policy scholar Rogan Kersh has noted, the problem “has proved impervious to clinical treatment or public-health exhortation,” and it is by no means clear what, if anything, public policy can accomplish, or what the best avenue for reform is, if indeed there is one. For an administration prone to smug castigation of its predecessors for their allegedly insufficient deference to scientific expertise, the Obama team is here shockingly cavalier about a scientific question of substantial depth and complexity. If Mrs. Obama, between her undergraduate major in sociology, her minor in African-American studies, and her law degree somehow managed also to acquire a great deal of expertise regarding a medical issue that has proved remarkably difficult for actual scholars and learned authorities, she has not seen fit to share how and where she acquired it.

Mrs. Obama’s “eat your veggies” crusade is at once a remarkably shallow response and a remarkably ambitious one: She may know next to nothing about the deeper issues, but she has adamant faith that the transformative quality of political power will allow even the most ignorant politician — or politician’s wife — to ameliorate any problem, even one that has thus far proved “impervious to clinical treatment.” By the same token, Mrs. Palin’s dismissal of that conceit contains more wisdom than is understood by political entrepreneurs of the Obama variety or by their factota in the media. Advantage: Palin.

First ladies have their causes, the general rule of which is that they do less damage the farther away from public policy they stay. If the Obama administration should happen to win the wars (and keep the won wars won) and balance the budget, head off the looming fiscal crisis, and present the American people with the head of Osama bin Laden, perhaps at that time it can get back to us about the broccoli. Until then, we have more of an appetite for Mrs. Palin’s healthy skepticism of governmental ambition than for Mrs. Obama’s overegged federal pudding: Washington has enough on its plate.