Four years after Chile embraced the world’s most sweeping measures to combat mounting obesity, a partial verdict on their effectiveness is in: Chileans are drinking a lot fewer sugar-laden beverages, according to study published Tuesday in the journal PLOS Medicine.

Consumption of sugar-sweetened drinks dropped nearly 25 percent in the 18 months after Chile adopted a raft of regulations that included advertising restrictions on unhealthy foods, bold front-of-package warning labels and a ban on junk food in schools. During the same period, researchers recorded a five percent increase in purchases of bottled water, diet soft drinks and fruit juices without added sugar.

“An effect this big at the national level in the first year is unheard-of,” said Lindsey Smith Taillie, a nutrition epidemiologist at the University of North Carolina, Chapel Hill, and the study’s lead author. “It is a very promising sign for a set of policies that mutually reinforce one another. This is the way we need the world to go to begin to really combat preventable diseases like obesity, hypertension and diabetes.”

The rules, adopted in 2016, were a bold gambit by the government of a country with some of the world’s highest obesity rates. Three-quarters of Chilean adults and more than half of children are overweight or obese, and health officials warned that the medical costs of obesity could consume 4 percent of the nation’s health care spending by 2030, up from 2.4 percent in 2016.

Since then, Peru, Uruguay, Israel have adopted Chilean-style front-of-package labels; Brazil and Mexico are expected to finalize similar labels in the coming months, and a dozen other countries are considering them as well.

The Chilean regulations were championed by then-president Michelle Bachelet, a socialist, and passed by the National Congress over fierce objections from big multinational food companies. Despite his initial opposition, Chile’s current president, Sebastián Piñera, a conservative billionaire businessman, has left the regulations in place.

The law is far-reaching. It includes mandatory package redesigns that erased cartoons like Tony the Tiger from sugary cereal boxes, and television advertising restrictions that banished ads for unhealthy products from the airwaves between 6 a.m. and 10 p.m. A study published last year by the journal Public Health Nutrition found that Chilean children were subjected to half as many ads for junk food and sugary drinks after the restrictions were put in place.

The regulations followed a 2014 measure that raised the tax on sugary beverages to 18 percent from 13 percent.

A centerpiece of the rules is a series of black stop signs that must appear on the front of packaged foods and beverages high in salt, sugar, fat or calories. Experts say the “high in” logos have had an unmistakable impact on the way Chileans shop for groceries. In focus groups, parents have described being reprimanded at the supermarket by their children if they reach for products emblazoned with the stop signs.

“Children are learning at an early age what types of food they should eat and which ones they should avoid,” said Dr. Camila Corvalán, a nutritionist at the University of Chile who also worked on the study. “We believe these regulations will change the way this new generation approaches eating, hopefully empowering them to demand healthier foods.”

The study, which tracked the purchasing habits of 2,000 households from 2015 to 2017, found that the drop in sugary-beverage consumption occurred both among the highly educated and those without a high school degree, although the reductions were somewhat greater among individuals who attended college.

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The food industry’s initial resistance to the measures has largely faded. To avoid having to display the dreaded stop signs on their products, companies like Nestlé, Coca-Cola and PepsiCo have reformulated hundreds of products, reducing the amount of sodium in salad dressings and substituting artificial sweeteners for sugar in carbonated drinks.

Asked to comment on the new study, a number of companies expressed a grudging acceptance of Chile’s laws but called for additional studies to assess their impact on obesity.

“We are committed to working with governments and other stakeholders to ensure that consumers have the information they need at their fingertips to support a balanced diet, and we offer a wide array of smaller-portion and lower or no-sugar options,” the International Council of Beverages Association said in a statement. A spokeswoman for Nestlé noted that the company had eliminated more than 3,000 tons of sugar from dairy products and breakfast cereals sold in Chile.

Experts say it is too soon to know whether the food regulations are making a dent in Chile’s obesity rates. But the early results could embolden policymakers in Chile. Barry M. Popkin, a University of North Carolina nutritionist who is advising the government, said legislators there are considering what he called a “mega tax” on processed foods — the frozen pizza, instant noodles and fast-food meals that are responsible for two-thirds of all calories consumed by children.

“Right now people are just focused on sugary beverages, which is a tiny part of the problem,” he said. “This is just the beginning of a fairly profound change to encourage healthy eating.”

Sara Bleich, a professor of public health policy at Harvard University who was not involved in the study, said the early results suggested that a raft of food policies, not just stand-alone measures like soda taxes, were needed to address a growing obesity crisis that is affecting nations rich and poor. “For countries hoping to move the needle on obesity, all eyes are on Chile,” she said, noting that half of American adults could be obese by 2030. “We need policies like these that are going to make a meaningful difference. And we need them now, not in five or ten years.”