Some years ago two nutrition experts went grocery shopping. For a dollar, Adam Drewnow­ski and S. E. Specter could purchase 1,200 calories of potato chips or cookies or just 250 calories worth of carrots. It was merely one example of how an unhealthy diet is cheaper than a healthy one. This price difference did not spring into existence by force of any natural laws but largely because of antiquated agricultural policies. Public money is working at cross-purposes: backing an overabundance of unhealthful calories that are flooding our supermarkets and restaurants, while also battling obesity and the myriad illnesses that go with it. It is time to align our farm policies with our health policies.

In past years farm subsidies have been a third rail of American politics—never to be touched. But their price tag, both direct and indirect, has now brought them back into the debate and created an imperative for change. Conditions such as heart disease, diabetes and arthritis are strongly correlated with excess poundage and run up medical bills of nearly $150 billion every year. The government has poured billions of dollars into dietary campaigns, from the U.S. Department of Agriculture’s new MyPlate recommendation (half of daily food consumption should be fruits and vegetables) to programs aimed at providing more produce in schools and in military cafeterias.

Agricultural subsidies undercut those efforts by skewing the market in favor of unhealthful calories. Much of the food we have to choose from—and how much it costs—is determined by the 1,770-page, almost $300-billion Food, Conservation, and Energy Act of 2008 (commonly known as the “farm bill”). This piece of legislation, up for renewal this year, covers everything from nutrition assistance programs to land conservation efforts. It also determines how much money gets paid out to agricultural operations in subsidies and crop insurance programs. Federal support for agriculture, begun in earnest during the Great Depression, was originally intended as a temporary lifeline to farmers, paying them extra when crop prices were low. Nearly eight decades later the benefits flow primarily to large commodity producers of corn and soy, which are as profitable as ever.

The current bill gives some $4.9 billion a year in automatic payments to growers of such commodity crops, thus driving down prices for corn, corn-based products and corn-fed meats. Cows that are raised on corn, rather than grass, make meat that is higher in calories and contains more omega-6 fatty acids and fewer omega-3 fatty acids—a dangerous ratio that has been linked to heart disease.

Cheap corn has also become a staple in highly processed foods, from sweetened breakfast cereals to soft drinks, that have been linked to an increase in the rate of type 2 diabetes, a condition that currently affects more than one in 12 American adults. Between 1985 and 2010 the price of beverages sweetened with high-fructose corn syrup dropped 24 percent, and by 2006 American children consumed an extra 130 calories a day from these beverages. Over the same period the price of fresh fruits and vegetables rose 39 percent. For families on a budget, the price difference can be decisive in their food choices.

But fruits and vegetables do not have to be more expensive than a corn-laden chicken nugget or corn syrup–sweetened drink. One reason they are costly is that the current farm bill categorizes them as “specialty crops” that do not receive the same direct payments or crop insurance that commodity crops do.

With the government tightening its belt, some of those old subsidies finally look ready to fall. Many lawmakers across the political spectrum, including President Barack Obama and the leaders of the U.S. Senate Committee on Agriculture, Nutrition and Forestry, have recommended cutting direct commodity payments, which would save money and help us stay healthier.

There is no dearth of policy options. Research groups such as the Robert Wood Johnson Foundation in Princeton, N.J., recommend leveling the playing field by extending subsidies and insurance programs more widely to fruit and vegetable producers. The government can also use its own purchasing power, through school lunch programs and institutional buying decisions, to fill people’s plates with healthy choices. The imperative, however, is clear: any new farm bill should at the very least remove the current perverse incentives for people to eat unhealthily.

This article was published in print as "Fresh Fruit, Hold the Insulin."