First Lady Michelle Obama made a splashy announcement yesterday with Wal-Mart and other supermarket executives regarding a planned expansion of fresh produce and healthy food offerings in 1,500 stores over the next five years. She lauded the idea, telling White House reporters, “Make no mistake about it. This is a big deal.” But is it?

If retailers see a rising demand for low-cost, healthy food, they should by all means capitalize on it. Yet cheap, nutritious groceries have long been available through a variety of outlets – even in so-called “food deserts.” It doesn’t mean consumers are clamoring to load up their grocery carts with veggies and whole grains. (So much for the simplistic “if you build it, they will come” solution.)

That’s exactly what a new study published in the Archives of Internal Medicine discovered when tracking the shopping habits of thousands of people over 15 years. As we told the Los Angeles Times, the problem has little to do with access to or pricing of healthy versus unhealthy foods, and much to do with consumer preference.

Consider the U.S. Department of Agriculture study from earlier this summer finding that carrots, sweet potatoes, apples, oranges, and bananas cost the same or less than less-nutritious fare like starchy vegetables and packaged snacks. And other healthy pantry staples – like eggs, beans, rice, canned or frozen vegetables, ground beef, and whole chickens – have always cost just a pittance per meal.

Time will tell whether this new supermarket strategy will make a major difference in the way Americans feed their families. But until other health factors are adequately addressed – like learning moderation in eating and promoting physical activity – we’re not holding our breath that Mrs. Obama’s latest push is going to amount to much in the checkout line.