A long-running contradiction in U.S. farm policy is fattening the waistlines of Americans and the profits of agribusiness at the same time. For the 30 years that the U.S. Department of Agriculture has been issuing dietary guidelines, there has been a stark inconsistency between the federal government's advice and its food funding.

True, the USDA has been doing more, over time, to promote health through dietary guidelines, food pyramids and other nutrition programs. And yet more than $20 billion yearly -- more than one-fifth its budget -- is sunk into a farm bill that supports many of the foods its recommendations warn against. At the same time, the department virtually ignores incentives to produce, promote and consume some of the healthiest foods: fruits and vegetables.

This contradiction may play a role in today's obesity epidemic and is in part driven by a counterintuitive farm policy, highlighted by the farm bill, which is up for renewal this year in Congress. This legislation began during the Depression to protect farmers against environmental disasters and plummeting crop prices but has evolved into a massive program of handouts, largely benefiting agribusinesses. Worse, it promotes vast overproduction of crops that are the building blocks of calorie-dense, nutrient-poor, processed junk foods. It has become a "food bill."

For a half-century, the farm bill served farmers and the public well by regulating supply and stabilizing food prices. In 1973, it was overhauled to significantly increase crop production. According to the USDA Economic Research Service, the U.S. food supply has since ballooned by 500 calories per person per day, and per capita food consumption has increased by more than 200 calories per day -- the equivalent of more than 20 pounds of fat per year.

This mammoth oversupply would be less egregious if it were spread equally among the food groups. Instead, most funding supports just a few crops, and those lay the foundation of the standard American diet: high in sugars and empty-calorie, refined grains; high in fats; low in whole grains and fiber; and low in fruits and vegetables.

Take corn, the most highly subsidized crop, which received $9.4 billion in 2005 -- nearly as much as all other crops combined. Corn production has more than doubled since the 1970s, and all this artificially cheapened corn is unloaded on the public, largely in the form of tasty but empty-calorie junk foods. Refined corn is the chief source of carbohydrates and calories in most processed foods, particularly snack foods. High-fructose corn syrup is the most widely used caloric sweetener in the United States. And corn meal is widely used as cheap animal feed to fatten factory-raised livestock.

Another example is soybeans, the fourth-most-subsidized crop. Although soy protein is a healthful meat substitute, soybeans are more commonly used in junk foods. Soybean oil accounts for 75 percent of the fat in processed foods and is commonly hydrogenated to create trans fats, which improve shelf life but are known to cause cardiovascular disease.

In contrast, healthful foods are grossly underfunded. USDA guidelines advise that fruits and vegetables make up at least one-third of daily intake, but just 5 percent of its food funding supports the fruit and vegetable industries. There is virtually no funding for public education and advertising encouraging fruit and vegetable consumption. At its peak, the "Five-a-day" campaign budget was just $3 million annually -- compared with the $11 billion spent yearly in the United States for fast food and junk food advertising. McDonald's spent $500 million just promoting its "We Love To See You Smile" campaign.

This is one reason Americans don't eat fruits and vegetables. Although some surveys suggest we eat about four servings daily, this number is greatly exaggerated because French fries and potato chips are counted the same as spinach, carrots or broccoli. In fact, 25 percent of vegetables consumed in the United States are fried potatoes, making the daily consumption of healthful fruits and vegetables closer to two servings -- and possibly lower in children and inner-city populations.

Farm policy is an ideal avenue to address the obesity epidemic at its roots.

As Congress considers this year's farm bill, it should rework the legislation so it meets the needs of today's food consumers, not agribusiness. The new farm bill should significantly shift funding to improve the availability, affordability and promotion of fruits, vegetables and other healthful foods.

In particular, it should include targeted investments to fruit and vegetable growers to increase the availability of fresh produce, support for the new "Fruits & Veggies -- More Matters" initiative, expansion of the Fresh Fruit and Vegetable Pilot Program to all 50 states to promote the eating of fruits and vegetables in schools, creation of incentives for fresh fruit and vegetable purchases in the Food Stamp program, and support for organic farming.

These steps could signal that our government is ready to lead the fight against obesity and diet-related chronic disease by nurturing the health-conscious lifestyle it advocates by its dietary guidelines.