Talk about throwing down a gauntlet.

In the March issue of Health Affairs, editor Susan Dentzer charges that “America is guilty of child abuse” for allowing almost one in three of its children to become either overweight or obese.

One of the causes of this obesity epidemic, she notes, is a U.S. agricultural policy “that has spurred production of cheap sugars and refined grains while doing little to encourage production of fruit and vegetables.”

The connection between our “cheap food” policy and our children’s alarming weight gain is explained in the current issue of Health Affairs by David Wallinga, MD, director of the Food and Health Program at the Minneapolis-based Institute for Agriculture and Trade Policy. I spoke with him on the topic last week.

How does U.S agricultural policy promote obesity?

For decades, U.S. agricultural policy hasn’t been based on health. It’s really been based on the idea of producing more … of a few commodity crops — things like corn and wheat and soybeans. … These were easy to grow and store and then ship by rail without refrigeration.

An after-the-fact priority was the recognition that a lot of people who joined the military during World War II were undernourished. There was a kind of simplistic thought that if we just ramped up the production of calories from those [commodity crops] we were already growing so well, we could give people enough calories — and they’d be healthier.

Science has shown, obviously, that it’s not as simple as that. The quality of the calories matters a lot. What we’ve done is create a generation of kids who are both overweight and undernourished because the calories they’re getting are not good ones.

Your numbers about how our daily caloric intake has increased are stunning, and soy and corn have played a big role in that, right?

Yes. Based on revised data collected by the [U.S. Department of Agriculture], the average American in 2007 was eating about 600 more calories than in 1970. Per day. And that’s the average. So you know that somebody who is supersizing a lot of meals and eating a lot of fast foods and junk foods is getting even more [added calories] than that.

The USDA also told us which categories of calories account for the increases. Added fat accounts for about one-quarter of the increase, and 70 to 80 percent of our fried fats and other oils come from soybeans. Another 8 percent of those oils are corn oils.

[Calories from] corn flour, corn meal, and other corn starches have also gone up hugely, including from the one [corn product] that most people think of — corn sweeteners.

If you look at table sugar, our consumption in the U.S. has actually gone down since 1970. But if you look at corn sweeteners as a replacement for table sugar, our consumption in terms of calories has gone up about 400 percent. [Wallinga points out in his Health Affairs paper that the average child now takes in 172 calories daily from sugar-sweetened beverages, including those sweetened with high-fructose corn syrup.]

So our oversupply of commodity crops has encouraged us to consume more calories, which has led to our current obesity epidemic. Are you comfortable calling it an epidemic?

Yes. It’s an epidemic both of the obesity and of the diseases closely related to obesity — such as diabetes, heart disease, stroke and cancer.

But there is an epidemic of health care costs, too. And that’s only going to get worse.

You note in your paper that current health policies for combating obesity tend to deal with “downstream” rather than “upstream” issues. Can you explain that?

The downstream approach is to say, well, if people are eating junky foods with a lot of added fats and sugars, then all we really need to do is educate them and somehow they’ll magically change their choices to better ones.

Nutrition education is important, but the other, upstream factors can’t be ignored. I would argue that in many cases, people are making perfectly rational food choices now. Our farm policies have made unhealthy calories the most affordable ones. So if you’re on a limited budget and you’re trying to get the biggest calorie bang for your buck, you’re going to supersize your meal at a fast-food restaurant and get a lot of corn- and soy-derived calories.

In inflation-adjusted terms, the calories in soda pop and in French fries fried in soy oil and in chicken nuggets made with corn meal and corn starch … have all decreased in price in real terms over the past 35 years. What’s gone up dramatically in real terms is the price of fruits and vegetables, especially fresh fruits and vegetables — exactly the kinds of foods that kids don’t eat enough of.

Those are the upstream choices we’ve made. The other thing that’s maybe worth mention is marketing. The USDA budget for marketing healthy foods like fruits and vegetables is miniscule compared to even one company’s budget for marketing soda pop. We could do all the education we want, but if there are huge marketing campaigns promoting unhealthy foods, what kind of an environment can we create for healthy choices?

But if we all started to eat the five to nine recommended daily servings of fruits and vegetables daily, would our farmers be able to meet the demand?

No, not right off the bat, because many of them are producing these other things. That’s how they pay their bills. But they could [produce enough fruits and vegetables], if they had the proper incentives. Our farmers have been really successful in responding to the policies and incentives that are given to them. But we don’t incent them to produce fruits and vegetables and other foods we really need in our diet.

You argue in your paper against the putative “quick fix” of eliminating farm subsides to commodity farmers, in part because it would erode our current supply of farmers, particularly those with mid-sized farms, who are the very ones needed to grow fruits and vegetables.

What I say is let’s make farmers our partners in producing a healthy diet for Americans. Let’s give them the incentives to produce fruits and vegetables and other healthy foods.

The alternative is to let American farmers keep producing what they’re producing now and to try and import the fruits and vegetables we need for a healthy diet.

But there are two problems with that. One is that it doesn’t provide the freshest produce. To ship produce long distance, it has to be picked early, maybe when it’s not ripe. And, of course, there are the issues of packaging and food miles and carbon costs.

But maybe the biggest problem [with importing most of our fresh fruits and vegetables from abroad] is a national security one. What happens in the future if countries decide not to ship to the United States or are prohibited from doing so? Where do we get our healthy foods from then?

The new Farm Bill is up in 2012. Are you hopeful that changes will be made in the bill that will help fight obesity?

Yes. We have two great things already going on. There’s the USDA’s "Know Your Farmer, Know Your Food" program, which is really trying to heal this disconnect between what people eat and where it comes from.

The other major positive thing is the White House. It’s got its new “Let’s Move” initiative on childhood obesity. Two of its four pillars deal with getting more healthy food to kids, one via schools and the other via encouraging more local fruit and vegetable production. So I’m very hopeful where that might lead.