New York Times science reporter Gina Kolata, who has an admirable record of questioning conventional wisdom about health issues, turns her skeptical gaze to the "food desert" hypothesis, which holds that poor people eat crappy diets and get fat because they do not have ready access to healthy comestibles such as fresh fruits and vegetables. As Kolata notes, this idea "has become an article of faith among some policy makers and advocates, including Michelle Obama," despite a lack of evidence to support it.

The website for the first lady's anti-obesity campaign, Let's Move!, brags that she "is taking on food deserts," which are "nutritional wastelands that exist across America in both urban and rural communities where parents and children simply do not have access to a supermarket." It claims that "some 23.5 million Americans—including 6.5 million children—currently live in food deserts." In a post on the Let's Move! blog, Rayne Pegg, administrator of the Agricultural Marketing Service, says "this lack of access contributes directly to poor diets which can lead to obesity" and plugs the Farmers Market Promotion Program, which aims to make fruits and vegetables more available by paying farmers to sell them. "For too many American families," says another post, "serving healthy food as part of a regular diet isn't actually an option. That's because, in many communities across the country, there is no place to purchase any groceries, much less fresh fruits and vegetables." The first lady explains that "it's not that people don't know or don't want to do the right thing; they just have to have access to the foods that they know will make their families healthier." That's why "eliminating these food deserts and making sure parents in every part of the country have access to fresh produce and healthy choices is a primary goal of Let’s Move."  

As Katherine Mangu-Ward noted in the February issue of Reason, these grand plans to make food deserts bloom seem to be based on some serious misconceptions. She highlighted a 2011 Archives of Internal Medicine study that found "proximity to a grocery store or supermarket did not increase consumption of healthy food." She suggested one reason geography is not dietary destiny: According to the USDA, "93 percent of 'desert' dwellers have access to a car." Kolata reports that recent research reinforces the case against the "food desert" hypothesis.

In one study, reported in the February issue of the American Journal of Public Health, researchers at the RAND Corporation used data on children and teenagers from the California Health Interview Survey to see if there was any association between diet and proximity to "fast-food restaurants, convenience stores, small food stores, grocery stores, and large supermarkets." They "found no relationship between what type of food students said they ate, what they weighed, and the type of food within a mile and a half of their homes." Kolata says Roland Sturm, co-author of the study, "has also completed a national study of middle school students, with the same result—no consistent relationship between what the students ate and the type of food nearby." He tells her "you can get basically any type of food" in almost any urban neighborhood, adding, "Maybe we should call it a food swamp rather than a desert." 

Another study, reported in the April issue of Social Science and Medicine, found that poor neighborhoods "had nearly twice as many fast food restaurants and convenience stores as wealthier ones," Kolata writes, but "they also had nearly twice as many supermarkets and large-scale grocers per square mile." The author, Helen Lee of the Public Policy Institute of California, reports that "differential exposure to food outlets does not independently explain weight gain over time" in the sample of elementary school students tracked by the Early Childhood Longitudinal Study. She writes that "it may thus be important to reconsider whether food access is, in all settings, a salient factor in understanding obesity risk among young children."

Even Kelly Brownell, the Yale psychologist who wants to tackle obesity through a system of taxes and subsidies that amounts to centrally planned food prices, scoffs at the notion that inadequate grocery options explain why poor people are disproportionately fat. "It is always easy to advocate for more grocery stores," he tells Kolata. "But if you are looking for what you hope will change obesity, healthy food access is probably just wishful thinking." When a grandiose social engineer like Brownell dismisses your plan to make Americans thinner as "wishful thinking," you really need to stop and consider whether your scheme has any connection to reality.

The Obama administration does not seem inclined to do that. Responding to Kolata's questions about the evidence indicating that the fight against food deserts is fundamentally misconceived, USDA spokesman Justin DeJong "said by e-mail that fighting obesity requires 'a comprehensive response'"—so comprehensive that it includes half-baked, empirically unfounded projects that are destined to fail. But we're doing other stuff too, says DeJong, such as (in Kolata's paraphrase) "improving food in schools, increasing physical education time, and educating people on the importance of healthy diets." Forcing kids to exercise in school (which is not necessarily what more time for gym would mean) might cause them to lose weight, assuming they do not respond by increasing their caloric intake or exercising less on their own time. But the goal of "improving food in schools" is based on the same questionable premise that gave us federal subsidies for farmers' markets: that people deviate from the government's dietary advice because they do not have access to healthy food, so eating properly "isn't actually an option," as Let's Move! puts it.

Similarly, "educating people on the importance of healthy diets" assumes they do not eat what the government thinks they should because they do not know any better. Yet anyone who shops for groceries can readily observe that some people pass up fresh fruits and vegetables, whole grains, lean protein, and skim milk, which they surely have heard are good for them, in favor of potato chips, white bread, ground beef, soda, and ice cream—not because the latter items are cheaper (they're not) but because they taste better (to these particular shoppers, at least). Michelle Obama and USDA bureaucrats probably have different tastes, and they certainly have different values and priorities. They are manifestly less willing to sacrifice their long-term health for the sake of short-term pleasure. When the first lady insists "it's not that people don't know or don't want to do the right thing," it is obvious to her what "the right thing" is: People need to eat less of the foods they like and more of the foods they don't. But to people with different preferences, this is not at all obvious, and it never will be, no matter how many fruits and vegetables the government throws at them.