Last month I discussed a front-page story by New Yorks Times science writer Gina Kolata debunking the notion that poor people eat poorly (and too much) because they live in poor neighborhoods with poor access to healthy food, a.k.a. "food deserts." Katherine Mangu-Ward noticed that on the very same day this article appeared, Times blogger David Bornstein was suggesting ways to make food deserts bloom. The headline on her post: "Food Deserts Are Not Real. Also, We Can Fix Them." Bornstein responded by backing away from the notion that food deserts, assuming they exist, have much to do with the (historically astonishing) inverse correlation between income and weight in 21st-century America. But in the process he endorsed another myth: that poor people eat poorly because they can't afford healthy food. Beginning with the acute insight that "the dominant constraint in the lives of low-income people is lack of money," Bornstein suggested that thriftiness is a major cause of obesity:

From 1985 to 2000, the prices of fresh fruits and vegetables rose 40 percent while prices of fats and soft drinks decreased by about 15 and 25 percent, respectively, noted Arielle E. Traub, a Senior Systems Analyst at the New York City Health and Hospitals Corporation in a report she wrote for the Johns Hopkins Bloomberg School of Public Health. Researchers have found that energy-dense foods (those that contain the most calories per gram, which is to say sweets and starchy foods) — are far less expensive than low-energy and nutritious foods like fruits and vegetables. In fact, measured on a per-calorie basis, they are one tenth the price. 

Hmm. "On a per-calorie basis"? Since junk food is dense in calories by definition, that measure pretty much guarantees it will come out looking like a bargain. A study released yesterday by the U.S. Department of Agriculture's Economic Research Service (ERS) takes a different approach, looking at price per edible gram and price per average portion as well as price per calorie. By those first two measures, it finds, "grains, vegetables, fruit, and dairy foods are less expensive than most protein foods and foods high in saturated fat, added sugars, and/or sodium." And despite all the talk about how expensive fruits and vegetables are, an earlier ERS study, based on 2008 data, found that "an adult on a 2,000-calorie diet could satisfy recommendations for vegetable and fruit consumption in the 2010 Dietary Guidelines for Americans (amounts and variety) at an average price of $2 to $2.50 per day, or approximately 50 cents per edible cup equivalent." The authors of the new ERS study note that total calories are a misleading measure of bang for your buck:

When making food choices, consumers may need to consider the entire cost of their diets. Cheap food that provides few nutrients may actually be "expensive" for the consumer from a nutritional economy perspective, whereas a food with a higher retail price that provides large amounts of nutrients may actually be quite cheap. Consumers should also consider the total daily cost—which is likely the one metric that will have the most relevance to consumers trying to control their food budgets. 

The lead author of the study cited by Bornstein, University of Washington epidemiologist Adam Drewnowski, defends the per-calorie method, telling the Associated Press, "Some of these calories are in fact empty calories, so from the standpoint of nutrition they are not terrific. But the empty calories keep you from being hungry, and this is why people buy them, especially lower-income people." Yet a 2007 New York Times story about Drenowski's study paraphrases him as saying that "it's easier to overeat junk food," partly because "eaters often must consume a greater volume in order to feel satisfied." Andrea Carlson, a co-author of the ERS study, tells A.P., "Using price per calorie doesn't tell you how much food you're going to get or how full you are going to feel." For instance, A.P. adds, "eating a chocolate glazed donut with 240 calories might not satiate you but a banana with 105 calories just might." If it's just a matter of feeling full, cheap, high-fiber foods such as beans, bananas, peas, sweet potatoes, brown rice, and whole-grain bread, pasta, or cereal look like a better deal than a bag of Doritos or a candy bar. And if it's all about cheap calories, shouldn't people be sucking down buckets of lard and bags of sugar?  

Explaining his calorie-centric view of food choices, Drenowski says (in A.P.'s paraphrase) "there is no government recommendation for how many pounds of food an American should eat each day, but there are federal guidelines that suggest a 2,000-calorie diet." So people who are fat because they routinely overeat and who show no interest in any other part of the government's nutritional recommendations are determined to hit that 2,000-calorie target at the lowest possible price? A visit to the grocery store will not reveal shoppers calculating prices on a per-calorie basis. Any calorie calculation will be working in the opposite direction, as weight-conscious consumers try to minimize their intake per serving and food manufacturers advertise the relatively low calorie content of their products—a puzzling phenomenon if consumers measure value by calories per dollar.

Obviously, not all shoppers are trying to minimize calories, but that doesn't mean they are trying to maximize them. Different consumers have different values, tastes, and preferences, and some would rather eat the calorie-dense foods they enjoy than forgo that pleasure for the sake of better health in the long run. Is that really so hard to comprehend?

Although price matters, a diet that complies with the government's guidelines is readily affordable—a fact that even the eager food nanny Mark Bittman recognizes. Bittman conceded in a New York Times column last fall that "it isn't cheaper to eat highly processed food," saying people who claim "junk food is cheaper than real food" are "just plain wrong." True, that was just two months after Bittman advocated government subsidies for dried legumes, one of the cheapest foods on the planet, in the name of "making healthy food more affordable." But if a fussie foodie like Bittman can see the reality that is on display every day at the local Walmart, there may be hope for public health researchers who insist that people prefer French fries and ice cream because they're cheap.