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One country and one strategy at a time, Latin America is waging war on obesity — and is winning.

In Chile, the Senate passed strict food-labeling laws. Mexico imposed a tax on sugary drinks and junk food, and Brazil opted for voluntary measures.

Infectious diseases are the leading causes of death in developing countries, but as economies grow, Western lifestyle factors such as high-fat diet, obesity and lack of exercise are emerging public health problems.

“The obesity epidemic is relatively new in Latin America,” said Camila Corvalán, a nutrition professor at the University of Chile who helped the Ministry of Health develop the policy. “But we knew exactly where we would end up. We have all the figures and numbers from the United States.”

By 2012, a quarter of schoolchildren and a third of Chile’s adult population were obese. Chile’s figures were not anomalous. U.S. percentage of obese children and adolescents has more than tripled since the 1970s, said the Centers for Disease Control and Prevention. And the most recent obesity estimates for adults approach 40%, the American Medical Association said.

In 2016, Chile started enforcing a law that included front-of-package warnings, restrictions on marketing unhealthful foods directly to children, and limits on what foods could be sold in schools and day-care facilities.

Guido Girardi, a physician who spearheaded the campaign, wrote in an e-mail: “The situation was producing an increase in noncommunicable chronic diseases and deaths. … And we have the conviction that this true tsunami of diseases affected the poorest who have a 160% higher risk of obesity, 380% higher risk of hypertension and 320% higher risk of diabetes and more than 100% higher risk of a heart attack … than people of high income.”

Foods high in added sugar, saturated fats, calories and added sodium must display black stop signs on labels. Nothing with black stop signs can be sold or promoted in schools or included in TV ads or marketing strategies aimed at children.

There was pushback.

“There was a very hard lobby,” Girardi said. In an episode that went viral on social media, a fast-food entrepreneur confronted Girardi on a flight, yelling, “You are the most nefarious thing that has happened to this country.”

The leading business lobby also weighed in, threatening to withhold money for sports teams and disabled citizens. Chilean President Sebastián Piñera moved to veto the law.

Girardi said a citizen scientific coalition eventually defeated the lobby but that companies such as Carozzi and Nestlé paid celebrities and athletes to malign the law. Spokesman Francisco Frei said Nestlé is complying with the rules. Carozzi did not comment.

Barry Popkin, a professor at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill, has been involved in policy formulation for Mexico, Chile, Brazil and Colombia and helped evaluate the initiative.

He said the program resulted in a reduction in the purchase of sugary beverages and a 9% decrease in the purchase of sugar-sweetened breakfast cereals. Many packaged foods have been reformulated in an attempt to avoid the black stop sign labels.

Uruguay and Peru have approved similar labeling.

Popkin said different strategies have proved effective in countries such as Mexico, which has a larger percentage of low-income citizens.

Between 1989 and 2006, sugary-drink consumption increased by 60%. Mexicans drank more soda per person than nearly any other country.

“The levels of obesity came as a shock,” said Juan Rivera, director of the National Institute of Public Health of Mexico. “On average, Mexicans were consuming 25% of all their calories from junk food and sugar-sweetened beverages.”

Part of the reason, Rivera said, was that Mexico had had a cholera epidemic in the 1990s and consumers were leery of tap water. People started buying bottled water — but if soda was even cheaper, why not pick the more flavorful beverage?

“We realized that if we had to take one single regulation, the perfect candidate would be sugar-sweetened beverages to overcome obesity,” Rivera said.

Rivera and other regulators found that increasing the price by 10% reduced consumption by 12%. Industry countered: This would hurt low-income people and the way to reduce obesity was more activity.

In Brazil, changing citizens’ nutritional behaviors has taken a voluntary route, which has also proved effective.

The guidelines also consider the impact of foods on the environment, unlike the U.S., which backed away from adding sustainability guidelines in 2015.

“Brazil’s guidelines are simple but radical,” said Jean Weinberg of Bloomberg Philanthropies, which funded obesity prevention programs in Mexico, Colombia, Brazil, Chile and Peru. “Choose whole, minimally processed foods, cook those foods yourself, and eat those foods with other people.

“The whole view of human rights is very different in Latin America. … They could still go back to their traditional diets and eating whole, healthy foods, and avoid where the U.S. has gone.”