RIO DE JANEIRO — Nutrition experts gathered here last week for the World Nutrition Rio 2012 meeting harped upon familiar themes: obesity and unhealthy food. Yet surprisingly many of them, in leading academic and government positions of public health, apparently have all but given up on tried-and-true public-health campaigns.

"Want to end obesity? Then talk to the ministries of finance, not health," said Philip James of the London School of Hygiene and Tropical Medicine and president of the London-based International Association for the Study of Obesity. "The impact of health education is zero."

The food industry is making us fat, according to James, and efforts to educate the public on proper nutrition or to ask industry to voluntarily reduce unhealthy ingredients such as sugar, salt, fat and myriad additives is "a load of diverting, delaying rubbish," he said. Government-initiated economic policies are needed to make healthy food affordable.

While James possesses a more extreme opinion among researchers at the meeting, he reflected a general tone of pure frustration among health experts in their efforts to tame the obesity pandemic. (In fact, a study out Monday, May 7, suggests by 2030, 42 percent of Americans will be obese.)

"There's not a country in the world where the obesity rate isn't climbing," said Barry Popkin, a renowned nutrition expert at the University of North Carolina at Chapel Hill, who presided over several talks. "China now has more children with diabetes than the United States."

Popkin explained how governments and multinational corporations shape diets on a global scale, from agricultural policies that favor the production of cheap sweeteners and meats, to the manufacturing of ultraprocessed foods that now dominate supermarket shelves. He has long advocated for a sugar tax on soda.

Carlos Monteiro of the University of São Paulo told meeting attendees that ultraprocessed food is "the biggest concern" in the obesity pandemic.

Monteiro introduced the term "ultraprocessed" in a 2010 commentary in the Journal of the World Public Health Nutrition Association. He characterizes foods as unprocessed, lightly processed and ultraprocessed. Unprocessed foods go from farm to fork with little handling; the only processing involves digestive juices in the mouth, stomach and intestines extracting nutrients from the food. Lightly processed foods are milled or pressed, as is done with grains and oils.

Ultraprocessed foods combine unprocessed and lightly processed foods with various additives to make food sweeter, saltier or richer, or to stay fresh for longer. They are generally nutrient-poor and calorie-dense snacks and ready-made meals. [7 Foods Your Heart Will Hate]

Few ultraprocessed foods existed before the 20th century, but now they comprise the majority of most diets, Monteiro said.

This presents a David-versus-Goliath scenario in which, increasingly, most people find it difficult to buy healthy food, experts say. A cycle develops in which people become dependent on processed foods, desiring their tastes or relying on their convenience; and then they lose the knowledge of how to prepare traditional, healthier, unprocessed foods. In this environment, health education can only go so far.

"I'm a great believer in regulation," said Marion Nestle, a professor of nutrition at New York University, joking more than once during the five-day meeting that she's not related to the Nestlé food corporation. "Just like with cigarettes, federal policy is needed on marketing. We have to confront the food industry, who try their best to make sure people eat more, not less."

Nestle advocates starting with agricultural support and pricing policies to encourage production and consumption of vegetables, fruits and whole grains. She said she also would like to see governments restrict marketing of junk foods to children on television, tax soft drinks, ban soft drinks and sugary drinks from schools, and mandate healthful school breakfasts and lunches. "These are worth a try, no," she asks rhetorically. [10 New Ways to Eat Well]

At one meeting session on traditional foods, Nestle highlighted her concern by showing a box of sweetened U.S. breakfast cereal sold in India with the prominent message that "good mothers" feed their children this cereal because it contains some of the nutrients found in dosa, a traditional Indian pancake of rice or lentils with no added sugar or salt.

The food industry has little incentive to police itself, the experts said, and government has been reluctant to force changes. While it is hard to envision change in food policy, it is not impossible.

"It's not about a lack of political will," said James. "That's nonsense. It's about poor political choices."

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on LiveScience.