Carlos Monteiro got his start in medicine in the 1970s as a pediatrician working in poor villages and slums in the state of São Paulo, Brazil. His patients were hungry, and it was written on their bodies: Many were anemic, underweight, and stunted. Today, Monteiro is a professor of nutrition at the University of São Paulo’s School of Public Health, a stately building surrounded by lush gardens. It’s a long way—figuratively, at least—from the shantytowns where he trained. His career has done a 180, too. Monteiro’s early research focused on malnutrition, but now he’s mostly occupied with the opposite problem: Brazilians, like most of their neighbors in the Americas, have gotten fat.

Over the course of his career, Monteiro, a lanky man with salt-and-pepper curls, has seen a public-health crisis emerge. In the mid-1970s, less than 3 percent of men and 8 percent of women in Brazil were obese. Today, almost 18 percent of adults are obese and more than half are overweight, according to the Ministry of Health, and the rates of chronic, diet-related diseases like diabetes and some cancers have grown. Monteiro has spent years parsing the data on what Brazilians eat; the most salient change he’s seen is the shift from eating foods you can prepare in an ordinary kitchen to what he calls “ultraprocessed products”—highly palatable admixtures of synthetic flavorings and cheap commodity ingredients that require little, if any, cooking. In other words, instant noodles, soda, and processed meats are edging out staples like beans and rice, cassava, and fresh produce.

“The local food system is being replaced by a food system that is controlled by transnational corporations,” Monteiro says. Monteiro, who takes a broad view of nutrition, says this dietary deterioration doesn’t just harm bodily health but also the environment, local economies, and Brazil’s rich food traditions. “We are seeing a battle for the consumer,” he adds.

Over the last 30 years, big transnational food companies have aggressively expanded into Latin America. Taking advantage of economic reforms that opened markets, they’ve courted a consumer class that has grown in size due to generally increasing prosperity and to antipoverty efforts like minimum-wage increases and cash transfers for poor families. And as sales of highly processed foods and drinks have plateaued (and even fallen, in the case of soda) in the United States and other rich countries, Latin America has become a key market. Between 2000 and 2013, soda sales in the region doubled. At the same time, the sales of ultraprocessed foods increased by nearly 50 percent, even as they rose just 2.3 percent in the United States and Canada.

Monteiro is part of a cadre of leaders who, in the face of this onslaught, are turning Latin America into a sort of food-policy laboratory. Some of the reforms they’ve enacted have also been proposed in the United States, but have been thwarted by the food industry and its political allies. Mexico, for example, enacted a tax on sugary beverages and junk food in 2014. Chile also taxes soda, and, like Ecuador, requires warning labels on unhealthy foods. Chile and Peru have also passed laws designed to strictly curtail the advertising of unhealthy foods.

Brazil, for its part, is a bit of a two-headed monster. On the one hand, its government has invested heavily in industrial agriculture, helping Brazil become one of the world’s largest exporters of soy and beef (as well as the top user of pesticides on the planet). But over the last dozen or so years, Brazil has also made huge progress against poverty and food insecurity while supporting the family farmers who produce 70 percent of the food that Brazilians eat. In 2014, the United Nations removed Brazil from its Hunger Map. It gave much of the credit to the zero-hunger policies of President Luiz Inácio “Lula” da Silva, who put ending hunger and poverty at the center of his agenda, building on strong social movements that had coalesced around nutrition issues and agrarian reform.

In recent years, Brazil has inscribed the right to food in its Constitution and reformed its federal school-lunch program to broaden its reach while bolstering local farms. And in 2014, the Ministry of Health released new dietary guidelines that made healthy-food advocates across the world swoon. Monteiro helped lead the team that wrote them; the guidelines transcend a traditional nutrition-science frame to consider the social, cultural, and ecological dimensions of what people eat. They also focus on the pleasure that comes from cooking and sharing meals and frankly address the connections between what we eat and the environment.

This is precisely the kind of holistic, unambiguous advice that US food reformers hoped to see in our new dietary guidelines, which were released in January. But for the most part, the latest version—which influences billions of dollars in government spending, the $5 trillion food industry, and the diets of millions of Americans—remains vague and narrowly focused, ensuring that no corporate ox was gored.

Nutrition advocates across the world are watching to see how these efforts play out in Brazil and elsewhere in Latin America. But there are strong headwinds. In Brazil, where some on the left have called the removal of President Dilma Rousseff “a coup against the poor,” there are worries that the country’s progress on hunger and food policy may unravel. Even before Rousseff’s suspension, the food movement was calling for more regulations and stronger action on land reform. It also called for stronger action to address the stubborn pockets of hunger in indigenous and other marginalized communities, says Maria Emília Pacheco, the head of the National Food Security and Nutrition Council (CONSEA), an influential group involved in making and monitoring policy that includes members of civil society and the government. Now, Pacheco warns, the neoliberal proclivities and austerity agenda of acting President Michel Temer could make it harder for the poor to afford healthy food, harm family farmers, or even put Brazil back on the Hunger Map.

Temer has already made some troubling moves. He sparked outrage when he eliminated the Ministry of Agrarian Development, which was dedicated to land reform and promoting family farming, distributing its duties among other agencies. His appointee for the Ministry of Agriculture is a soybean baron who has proposed weakening the legal definition of working conditions that constitute modern-day slavery.

Still, despite worries, there have been no big cuts to Bolsa Família—the welfare program that gives cash to some 14 million poor households monthly—though a Cabinet member has said the rolls will be closely examined for fraud and could shrink by as much as 10 percent. And in July, Temer announced an increase in families’ payments that actually surpasses the one Rousseff promised last spring. At the same time, while Temer’s antitax stance makes it unlikely that Brazil will get a Mexico-style soda tax on his watch, the interim health minister did recently announce that the ministry is banning the sale of unhealthy ultraprocessed products in its offices and in the hospitals it administers, which include Brazil’s National Cancer Institute.

As many people I spoke with pointedly reminded me, Rousseff’s fate is not yet decided. But at least one thing is clear: Whatever the political outcome, Latin America’s food industry isn’t backing down. In recent years, in fact, it has been increasingly organized, fighting regulations in an ever more coordinated way. Trade groups from several countries have banded together as the Latin American Food and Beverage Alliance, and have been joined by the powerful US-based Grocery Manufacturers Association, which has fought efforts to ban soda sales at schools and restrict food advertising that targets children. The alliance opposes taxes and marketing restrictions that authorities like the Pan American Health Organization (PAHO) recommend, instead advocating voluntary measures that health experts say are often inadequate and impossible to enforce.

“We are in a very intense time, in terms of food and nutrition in Latin America,” says Enrique Jacoby, a physician who served as Peru’s vice minister of health and also worked on food policy for years at PAHO. Jacoby says that reform efforts have been generally popular, particularly when framed as protecting children. But the industry has had some big wins, successfully weakening proposed rules or stalling them with legal challenges. “The food industry is fighting fiercely to prevail,” Jacoby says.

* * *

On a hot afternoon in the industrial city of Guarulhos, Maria de Lourdes Coelho huffs a little as she pushes her cart up a steep grade. Coelho is a door-to-door saleswoman for Nestlé, one of about 6,000 nationwide. Nestlé began deploying these sellers 10 years ago as a way to get its products—things like yogurt, candy bars, and instant noodles—into the hands of lower-income consumers. At the top of the hill, Coelho’s customers, a young couple with a toddler, are waiting. They ordered two variety packs of sweetened yogurts and puddings; the man says his daughter asks for the yogurt by name.

“Say, ‘Na-no-ni-no,’” he coaches the little girl. “Na-no-ni-no…” He’s trying to get her to say “Danonino,” which is actually the name of a product sold by Nestlé’s competitor Dannon, but the word has become shorthand for a thick, sweet yogurt that comes in tiny cups and is adored by little kids. The baby, alas, has stage fright, so the father gives up and pays Coelho.

Heading downhill, Coelho says, “That was a good sale.” Customers don’t have to pay right when they get the product; the retail model caters to poorer customers by giving them two weeks to pay. (Unfortunately for Coelho, it’s the sellers who eat the loss if customers default.) The model is particularly popular on the urban periphery, where there are few supermarkets. Nestlé entices customers with gifts like cell-phone minutes and Frozen-themed backpacks.

As the door-to-door sales helped Nestlé reach new customers in the city, the company turned in 2010 to the Amazon region, where it launched a floating supermarket. The boat—christened the “junk-food barge” by detractors—docks in riverside communities and sells a range of Nestlé products, often in smaller, cheaper packages than are typically found in grocery stores. Nestlé representatives would not provide me with any information about the boat’s location, saying only that the program is “currently being revised.” They did, however, say that its door-to-door sales and floating supermarket—emblazoned with the words “Nestlé comes to you!”—help meet consumer demand and create jobs, many of them for women.

* * *

The image of Nestlé’s big blue boat steaming along the Amazon River is an apt, if unsubtle, illustration of the way that Brazilian diets have changed during Monteiro’s career. As he has watched manufactured food products displace cooked foods, he’s come to believe that nutritionists need to overhaul the way they think and talk about healthy diets.

Comparing data on grocery spending by households in 1987 and 2003, Monteiro noticed something curious. Sales of table sugar and soy oil, which had accounted for much of the fat and added sugar in people’s diets, were down. That fit nicely with the diet advice nutritionists were giving at the time. But the rates at which Brazilians were being measured as obese or overweight were still on the rise. The data also showed that people were consuming less beans, rice, milk, eggs, flour, and produce.

So what were they eating? Foods that came ready to eat or nearly so. Households consumed more than twice as much processed meat and dairy—such as sausages and sweet milky drinks—in 2003 as they did in 1987. Soda consumption doubled, and purchases of “cereal products” like bread and cookies had also increased.

Monteiro came to believe that nutritionists’ traditional focus on food groups and nutrients like fat, sugar, and protein had become obsolete. The more meaningful distinction, he started to argue, is in how the food is made. Monteiro is most concerned with the “ultraprocessed products”—those that are manufactured largely from industrial ingredients like palm oil, corn syrup, and artificial flavorings and typically replace foods that are eaten fresh or cooked. Even by traditional nutritionists’ criteria, these sorts of products are considered unhealthy—they tend to be high in fat, sugar, and salt. But Monteiro argues that ultraprocessed foods have other things in common: They encourage overeating, both because they are engineered by food scientists to induce cravings and because manufacturers spend lavishly on marketing.

The focus on processing also widens to include issues like social norms and the environment, which have typically fallen outside the purview of nutrition science. Many processed foods are made to be eaten on the run or as snacks, which erodes the tradition of family meals. And the manufacture of these products is tied to the industrial farming of staples like corn and soy instead of the produce of family farmers, says Fabio Gomes, a nutritional adviser at PAHO who has collaborated with Monteiro.

Since defining the term “ultraprocessed products,” Monteiro and his colleagues have published papers suggesting that people whose diets contain a larger proportion of them are more likely to be overweight or obese, though studies like these can’t determine causality. A recent PAHO report looked at data from 14 countries and found that, as a country’s per-capita sales of ultraprocessed products rose, so did its obesity rates.

But even if the data suggest that ultraprocessed products are driving the increased obesity rates, where does that leave the average consumer? Many families can’t afford to return to a time when one person stayed home and cooked for everyone, even if they wanted to.

But Monteiro says the demands of modern life don’t have to mean abandoning real food. He points to Brazil’s ubiquitous per-kilo restaurants, which serve fresh home-style dishes to diners who pay by weight. There are also opportunities to bring more fresh food into institutional settings like schools, hospitals, and the military.

Lorena Rodríguez, who leads the food-and-nutrition department in Chile’s Health Ministry, says she’s been deeply influenced by Monteiro’s work. Like him, she promotes cooking, but says no one is trying to return to a time when women had no choice but to serve as the family’s cook. Nutrition educators have been working with communities to start a dialogue not just about how people should eat, but how they should share the responsibility. “This is the work of everyone,” she says. “It is not that we women are going to return to the kitchen. We are all going back to the kitchen together.”

* * *

Monteiro spends a lot of time looking at what’s wrong with the Brazilian diet, but says some things are headed in the right direction. Brazil’s school-lunch policy, which has become central to addressing hunger and poverty, is “an example for the world,” he says: Students get healthy meals, while family farmers, who are often at risk of poverty themselves, get access to a huge and consistent market.

To see for myself, I visit a public school in São Paulo’s Perus district. In one of the school’s two kitchens, a pressure cooker hisses steam while four cooks crack eggs and chop sweet potatoes and zucchini. The day’s menu: vegetable frittata with beans and rice.

As she washes bunches of parsley, Sonia Silvia dos Santos tells me the cooks make almost everything from scratch. They cut up big slabs of meat and whole chickens and use very few ultraprocessed ingredients. Even bouillon cubes are verboten: “Just onion, garlic, salt, and parsley,” she says. “Natural things.”

Brazilian law guarantees each public-school student—from nursery school to adult education—at least one free meal each day and also stipulates that 70 percent of federal school-lunch funds must go to basic foodstuffs that are natural or not highly processed. Lula’s administration improved the nutritional quality of meals and, in 2009, passed a law requiring that 30 percent of federal school-lunch funds be spent on food produced by family farmers, with preference given to indigenous farmers, descendants of slaves, and beneficiaries of agrarian reform. The support of the food movement, which has become broader and stronger over the last decade, was crucial in getting the law passed. And today, public participation remains central: the law requires that councils made up of parents, students, and government representatives monitor school-lunch programs to make sure they’re providing safe, healthy meals and spending the money properly.

Once lunch is served, a group of students sits at a table with their teacher, Shirley Suarez do Carmo. She cajoles a few kids into trying the frittata. “Sometimes kids don’t want to try things,” she says. “But when they see their teacher eating it, they want to try it, too.”

The scene in this lunchroom is pretty idyllic, but not all students are so lucky. Some schools aren’t buying as much from small farmers as the law requires (though other districts are surpassing the minimum). And Brazil’s school-lunch program hasn’t been immune to corruption—in fact, Temer’s current transportation minister was convicted in 2014 of improperly diverting school-lunch funds. A “school-lunch mafia” is under investigation in São Paulo state for allegedly running a kickback scheme in which a farm cooperative would overcharge the state and some municipalities, then pay “tips” to officials.

Still, the school-lunch law has been “a revolution” for family farmers, says Serge Dominguez de Ramos. Dominguez works for a cooperative that has been supplying the school district with bananas for the last year and a half. The co-op’s 1,500 families have seen their income more than double, and there’s new hope that the family-farm sector, after struggling for years, may be viable after all. “Before, farmers were going to the cities, and they were earning the minimum of the minimum because they didn’t have an education,” Dominguez says. “Now, they’re coming back to the countryside.”

* * *

Many of the principles that underlie Brazil’s school-lunch program—the focus on real food, the cultural importance of meals, and the support for family farmers—formed the bedrock of Brazil’s nutritional guide, released in 2014. The resulting document went far beyond typical dietary advice, prompting gushing headlines like this one from Vox: “Brazil has the best nutritional guidelines in the world.”

Having worked closely with Monteiro on nutrition issues for years, the Health Ministry contracted him and a group of his colleagues and graduate students to write the guide. Early on, the group decided to address the public, not just nutritionists. “People don’t need to understand the difference between saturated fats and unsaturated fats,” Monteiro says. “We don’t think normal people will decide what to eat based on nutrients.”

The guide recommends avoiding ultraprocessed foods and gives a detailed description of how these products harm physical health, social life, and the environment. Given the food industry’s power, it was a “courageous” move, says CONSEA’s Pacheco, who gave feedback on the guidelines, which were also open to public comment. While she would have liked to have seen more attention paid to regional food differences and the way food choices can affect biodiversity, Pacheco considers the guide “an important step forward.”

Pleasure is an essential part of the new guide, which frames cooking as a time to enjoy with family and friends, not a burden. And instead of sterile prescriptions for the number of grams of fat and fiber to eat each day, the guide focuses on meals. Sample meals were created by looking at the food habits of Brazilians who eat the lowest amount of ultraprocessed foods. One dinner option is a vegetable soup followed by a bowl of acai pulp with cassava flour, as one might eat in the Amazon region. Another plate, more typical of São Paulo, is spaghetti, chicken, and salad. If these seem like ordinary meals, that would be the point, one of the researchers said: They wanted to counteract the idea that a “healthy” diet is one full of unfamiliar and even unpleasant foods.

A big difference between the Brazilian and US guidelines is the way they handle the question of sustainability. The Brazilian guide defines healthy diets as those that “derive from socially and environmentally sustainable food systems,” and it warns that family farms—one such sustainable system—are being displaced by industrialized farms reliant on mechanization and monoculture. The guide also addresses the environmental impact of one of Brazil’s main exports: beef. While it doesn’t criticize the meat industry as strongly as it does ultraprocessed foods, the guide encourages a diet based mainly on plants, stating that limiting foods derived from animals will reduce greenhouse-gas emissions, deforestation, and water use.

The US guidelines, on the other hand, make no mention of sustainability. The expert panel that advised the Departments of Agriculture and Health and Human Services, which formulated the guidelines, recommended that sustainability be addressed, particularly in relation to meat consumption. But the powerful meat industry launched a lobbying campaign that ultimately kept sustainability concerns out of the guidelines.

Barry Popkin, a nutrition researcher at the University of North Carolina, Chapel Hill, and a longtime collaborator of Monteiro’s, says Brazil’s guidelines are “very interesting and very ambitious,” but he doesn’t think they’ll cause much change on their own, since people all over the world are eating more ultraprocessed foods, not less. “Can you just stop it with guidelines like Carlos’s?” he asks. “No, you have to do serious things.”

Among the “serious things” Popkin wants to see are higher taxes on sugary drinks and restrictions on kid-targeted advertising—measures that Monteiro also favors. But even if the guidelines don’t have legal weight themselves, PAHO’s Gomes says they lay the groundwork for policymaking that will have the force of law.

In the past, Brazil has tried to enact more ambitious policy changes, like a 2006 proposal that would have limited food advertising directed at children and required warnings on ads for unhealthy foods. A weakened version was adopted in 2010, only to be stalled by industry opposition. The industry has also managed to weaken or forestall regulations in other countries, says Jacoby, although this opposition was fairly uncoordinated at the regional level until about three years ago, when the Latin American Food and Beverage Alliance was formed.

Mary Sophos, the senior vice president of government affairs at the Grocery Manufacturers Association, says that she can’t speak for the other alliance members. But she does describe her own group’s approach to regulations, which is echoed in alliance documents: “We think the most important thing is that the rules and regulations or guidelines be science-based. The obesity crisis is real and it needs a solution, so if we could stick to science- and evidence-based policies, we are more likely to make progress.”

Sophos declined to give examples of specific healthy-eating policies that are not based in science, saying the question is “too much of a hypothetical.” Asked to respond to this critique, Monteiro’s irritation is clear. After reiterating his credentials as a physician, a nutritionist, and a researcher with 40 years’ experience and some 200 scientific papers published, he says: “I know what science is. They are not the ones that should be questioning whether our research is science-based or not. They simply don’t have the authority.”

* * *

T he battle over food policy in latin America is likely to continue—and it could have repercussions worldwide. Health advocates in many countries have been watching Mexico’s soda tax closely, and Jacoby says he expects to see similar taxes proposed elsewhere in Latin America. When Berkeley, California, became the first US city to institute a soda tax, in 2014, campaigners drew heavily on the Mexican experience. In June of this year, Philadelphia became the second city to adopt a soda tax.

But Popkin says that it is lower- and middle-income countries that will continue to lead on food-policy reform, and he cites new efforts in Chile, Thailand, India, and South Africa as particularly promising. “There’s no high-income country in the world that’s doing much,” he says, adding that economics is a big part of the reason. While the United States has managed to largely ignore the huge costs of diet-related diseases, lower- and middle-income countries don’t have that luxury.

There are social reasons, too, Monteiro points out. Brazil’s dietary guidelines had strong support in the healthy-food movement, in part because it was involved in their creation. When the food industry tried to block the guide’s release, this support saved it. “Without this, it would have been impossible,” he says.

And even though traditional diets are threatened by the rapid rise of junk food, no Latin American country has lost its food traditions altogether. “In Latin America, we still cook. We love our culinary traditions,” says Jacoby, whose own country, Peru, has a food culture that’s deep and beloved. Even so, he emphasizes, this culture has to be defended. “It took us probably 500 or 600 years to create these food traditions. But the food industry could come and destroy this all in 10 years.”