ANAHEIM, Calif.

AS tens of thousands of people recently strolled among booths of the nation's largest organic and natural foods show here, munching on fair-trade chocolate and sipping organic wine, a few dozen pioneers of the industry sneaked off to an out-of-the-way conference room.

Although unit sales of organic food have leveled off and even declined lately, versus a year earlier, the mood among those crowded into the conference room was upbeat as they awaited a private screening of a documentary called "Food Inc." - a withering critique of agribusiness and industrially produced food.

They also gathered to relish their changing political fortunes, courtesy of the Obama administration.

"This has never been just about business," said Gary Hirshberg, chief executive of Stonyfield Farm, the maker of organic yogurt. "We are here to change the world. We dreamt for decades of having this moment."

After being largely ignored for years by Washington, advocates of organic and locally grown food have found a receptive ear in the White House, which has vowed to encourage a more nutritious and sustainable food supply.

The most vocal booster so far has been the first lady, Michelle Obama, who has emphasized the need for fresh, unprocessed, locally grown food and, last week, started work on a White House vegetable garden. More surprising, perhaps, are the pronouncements out of the Department of Agriculture, an agency with long and close ties to agribusiness.

In mid-February, Tom Vilsack, the new secretary of agriculture, took a jackhammer to a patch of pavement outside his headquarters to create his own organic "people's garden." Two weeks later, the Obama administration named Kathleen Merrigan, an assistant professor at Tufts University and a longtime champion of sustainable agriculture and healthy food, as Mr. Vilsack's top deputy.

Mr. Hirshberg and other sustainable-food activists are hoping that such actions are precursors to major changes in the way the federal government oversees the nation's food supply and farms, changes that could significantly bolster demand for fresh, local and organic products. Already, they have offered plenty of ambitious ideas.

For instance, the celebrity chef Alice Waters recommends that the federal government triple its budget for school lunches to provide youngsters with healthier food. And the author Michael Pollan has called on President Obama to pursue a "reform of the entire food system" by focusing on a Pollan priority: diversified, regional food networks.

Still, some activists worry that their dreams of a less-processed American diet may soon collide with the realities of Washington and the financial gloom over much of the country. Even the Bush administration, reviled by many food activists, came to Washington intent on reforming farm subsidies, only to be slapped down by Congress.

Mr. Pollan, who contributes to The New York Times Magazine, likens sustainable-food activists to the environmental movement in the 1970s. Though encouraged by the Obama administration's positions, he worries that food activists may lack political savvy.

"The movement is not ready for prime time," he says. "It's not like we have an infrastructure with legislation ready to go."

Even so, many activists say they are packing their bags and heading to Washington. They are bringing along a copy of "Food Inc.," which includes attacks on the corn lobby and Monsanto, and intend to provide a private screening for Mr. Vilsack and Ms. Merrigan.

"We are so used to being outside the door," says Walter Robb, co-president and chief operating officer of Whole Foods Market, the grocery chain that played a crucial role in making organic and natural food more mainstream. "We are in the door now."

AT the heart of the sustainable-food movement is a belief that America has become efficient at producing cheap, abundant food that profits corporations and agribusiness, but is unhealthy and bad for the environment.

The federal government is culpable, the activists say, because it pays farmers billions in subsidies each year for growing grains and soybeans. A result is an abundance of corn and soybeans that provide cheap feed for livestock and inexpensive food ingredients like high-fructose corn syrup.

They argue that farm policy - and federal dollars - should instead encourage farmers to grow more diverse crops, reward conservation practices and promote local food networks that rely less on fossil fuels for such things as fertilizer and transportation.

Last year, mandatory spending on farm subsidies was $7.5 billion, compared with $15 million for programs for organic and local foods, according to the House Appropriations Committee.

But advocates of conventional agriculture argue that organic farming simply can't provide enough food because the yields tend to be lower than those for crops grown with chemical fertilizer.

"We think there's a place for organic, but don't think we can feed ourselves and the world with organic," says Rick Tolman, chief executive of the National Corn Growers Association. "It's not as productive, more labor-intensive and tends to be more expensive."

The ideas are hardly new. The farmland philosopher and author Wendell Berry has been making many of the same points for decades. What is new is that the sustainable-food movement has gained both commercial heft, with the rapid success of organic and natural foods in the last decade, and celebrity cachet, with a growing cast of chefs, authors and even celebrities like Oprah Winfrey and Gwyneth Paltrow who champion the cause.

It has also been aided by more awareness of the obesity epidemic, particularly among children, and by concerns about food safety amid seemingly continual outbreaks of tainted supplies.

While their arguments haven't gained much traction in Washington, sustainable-food activists and entrepreneurs have convinced more Americans to watch what they eat.

They have encouraged the growth of farmers' markets and created such a demand for organic, natural and local products that they are now sold at many major grocers, including Wal-Mart.

"Increasingly, companies are looking to reduce the amount of additives," says Ted Smyth, who retired earlier this year as senior vice president at H. J. Heinz, the food giant. "Consumers are looking for more authentic foods. This trend absolutely has percolated through into mainstream foods."

While the idea of sustainable food is creeping into the mainstream, the epicenter of the movement remains the liberal stronghold of Berkeley, Calif.

It was there in 1971 that Ms. Waters started a restaurant, Chez Panisse, that used fresh, organic and locally grown products, a novelty at the time that has been widely copied by other chefs. In the years since, she has become a food celebrity, the "mother of slow food," as a "60 Minutes" profile called her.

Mr. Pollan teaches journalism at the University of California, Berkeley, and is among a group of authors who have tapped into a wide audience for books that encourage local or organic foods while detailing what they view as health and environmental risks of processed foods and large-scale agriculture.

His book "The Omnivore's Dilemma" has remained on best-seller lists since it was published in 2006. Another activist, Eric Schlosser, wrote "Fast Food Nation," a critical look at industrialized fast food that was published in 2001 and is now required reading at some colleges. And Marion Nestle, a nutrition professor at New York University, has become a ubiquitous and widely quoted critic of commercial food manufacturers.

Beyond authors, academics and chefs, the sustainable-food movement also owes much of its current success to pioneers in the organic and natural foods industry. Many started their businesses for idealistic reasons and have since turned their start-ups into multimillion-dollar, even billion-dollar, corporations.

Manufacturers improved their organic and natural products, long confined to musty natural-food stores, so they could compete with conventional foods on packaging and taste. Whole Foods Market also lured more mainstream customers by redefining what a grocery store should look like, creating lush displays of produce and fish that have influenced more traditional grocers.

Nancy M. Childs, a professor of food marketing at St. Joseph's University, said sustainable food activists forced the broader public to focus on the quality and sourcing of food, which in turn has prompted demand for farmers' markets and local produce. She says that "continual attention in the news" also gave the movement legs.

But Ms. Childs worries that some of the activists' recommendations for buying fresh, local or organic food cannot be adopted by many Americans because those foods may be too expensive. "By singling out certain lifestyles and foods, it's diminishing very good quality nutrition sources," she says. "Frozen goods, canned goods, they are not bad things. What's important is that people eat well, within their means."

"We'd all love to live on a farm in Vermont, right?" she adds.

Even Jeffrey Hollender, the president of the green cleaning-products company Seventh Generation, worries that some of his movement's messages are a tough sell when consumers are stretched thin.

Although some people argue that there are hidden costs to cheap food, from environmental damage caused by factory farms and fertilizer runoff to the health costs associated with eating highly processed, calorie-laden food, the fact remains that commercially produced food is relatively inexpensive.

"The idea of the true cost of food?" Mr. Hollender asks. "That's the last thing consumers want to hear right now."

The sustainable-food crowd isn't alone in its love fest with the Obama administration and Mr. Vilsack. Food-safety activists have praised Mr. Vilsack's remarks about creating a single food-safety agency, and nutrition advocates are enthused about his comments on school lunches and health care reform.

"There are tremendous opportunities with health care reform," says Michael F. Jacobson, executive director of the Center for Science in the Public Interest. "Cutting sodium consumption in half should save over 100,000 lives a year."

THERE is little in Tom Vilsack's r�sum� to suggest that he would one day be lionized by America's food glitterati.

A native of Pittsburgh, he became a small-town mayor and lawyer in Iowa, where he represented struggling farmers during the farm crisis in the 1980s. As a state senator and later as governor of Iowa, Mr. Vilsack promoted ethanol production and agricultural biotech, leading one consumer group to label him a "shill" for Monsanto.

When a coalition of food activists and farmers, Food Democracy Now, circulated a petition urging President Obama to pick an agriculture secretary committed to sustainability, Mr. Vilsack was not one of its recommended candidates.

Mr. Vilsack said that he was a chubby child and maintains a deep affection for cookies. But something has changed in Mr. Vilsack, an avid runner, including his eating habits. "I'm much more inclined to eat fresh fruits and vegetables," he says. "I had organic yogurt for breakfast. Trust me, I would have not have had that two years ago, or four years ago."

He was motivated to eat healthier because he is expecting his first grandchild and regrets that his parents did not live to meet his own children.

Mr. Vilsack's brief tenure at the agriculture department has unnerved the food lobby and cheered sustainable-food activists, who are in agreement with many of his stated priorities.

He has said he hopes to devote more resources to child nutrition to improve the quality of school breakfasts and lunches. He also wants to make sure that only healthy choices are available in school vending machines.

Noting that the department's recently released Census of Agriculture included more than 100,000 new small farmers, he said he wanted his agency to help them develop regional distribution networks. The small farms' produce could be sold to institutional buyers like schools.

Ultimately, he said, agriculture and food policy should fit into the Obama administration's planned overhaul of health care, by encouraging nutrition to prevent disease. It should also be part of the effort to combat climate change, by encouraging renewable energy and conservation on farms, he said.

Of course, Mr. Vilsack will need the approval of Congress for any major changes in farm policy, and therein lies his greatest challenge. Congress passed a farm bill last year that details farm policy for the next five years, and farm-state legislators say they are not interested in starting over.

When the Obama administration recently proposed a budget that would cut subsidies to the nation's largest farmers and bolster child nutrition payments, it was greeted with hostility in Congress, even by some Democrats.

It didn't help that Mr. Vilsack framed the budget as a choice between helping 90,000 farmers or 30 million children, a statement that he later characterized as inartful.

Representative Frank D. Lucas, Republican of Oklahoma and the ranking minority member of the House Agriculture Committee, said in a statement that "this proposal is ill-timed, ill-conceived and completely out of touch with the realities of agriculture production."

FOR all the enthusiasm that sustainable-food activists and celebrities have for the Obama administration, their sudden interest in Washington has already ruffled feathers.

Ms. Waters wrote a letter to the Obamas in January suggesting that she convene a "kitchen cabinet" to pick a suitable chef for the White House, "a person with integrity and devotion to the ideals of environmentalism, health and conservation." Her letter touched off withering criticism in the blogosphere, with one food pundit blasting what he called Ms. Waters's "inflexible brand of gastronomical correctness."

The Obamas stuck with the existing chef, who it turns out was already an ardent - though quiet - proponent of locally grown food.

In addition, some sustainable-farm advocates who have worked on these issues for decades in Washington are chafing at the idea of celebrity activists swooping into town.

Ferd Hoefner, policy director of the Sustainable Agriculture Coalition, says that during the Carter administration he fought to get $5 million in federal money to promote farmers' markets (about the same as allocated last year).

While he acknowledges that it has been an uphill fight, Mr. Hoefner said the activists had made major strides in recent years, winning more federal dollars for organic research and to help farmers convert to organic methods and add value to their operations by, for example, converting to grass-fed beef. As part of the economic stimulus plan, the Agriculture Department also plans to award $250 million in loan guarantees, spread over the next two years, for local and regional food networks, he said.

Mr. Hoefner said he was impressed by the number of people who rallied for a White House garden. "We just want to make sure that interest in that symbolic action can be channeled into some of the more difficult policy challenges," he said.

Senator Tom Harkin, Democrat of Iowa and chairman of the Senate Agriculture Committee, welcomes newcomers to the cause but cautions that farm policy "does not have sharp turns."

Mr. Harkin has spent years trying to increase federal dollars for child nutrition and for conservation programs that reward farmers for protecting the environment, relatively small programs that he says can expand under the Obama administration.

"We bend the track a little bit and get the train going in a little bit different direction," he says. "We're hoping we can bend it a little bit more. Consumers are demanding it."

There are already signs that the sustainable-agriculture track is bending farther than before. The conservative pundit George F. Will wrote a column endorsing many of Mr. Pollan's ideas, and a prominent food industry lobbyist who requested anonymity because he wasn't authorized to speak to reporters said he was amazed at how many members of Congress were carrying copies of "The Omnivore's Dilemma."

"I'm not sure how much it's penetrating the mom shopping at Food Lion," he says. "I've had so many members mention Michael's name to me, it's staggering."

Back in Anaheim, Mr. Hirshberg, the head of Stonyfield Farm, said he, too, is optimistic that change is at hand. But he reminded the small crowd that the organic industry remains a "rounding error," roughly 3 percent, of the overall food and beverage business.