A man rides his bicycle past a billboard of the late Fidel Castro in Santa Clara, Cuba. (Ivan Alvarado/Reuters)

Fidel Castro’s long and powerful influence over Cuba produced many well-known geopolitical events, from the Bay of Pigs invasion to the Cuban missile crisis. The Castro years also included a unique but little recognized public-health phenomenon. In the early and mid-1990s, the Cuban population became the only modern society to lose significant weight on a national basis.

As Cuba’s citizens lost weight, their rates of diabetes and heart disease plummeted. When the weight came back roughly a decade later, diabetes and heart disease resumed their insidious attacks. “We were able to analyze weight and health in Cuba for three decades,” says Manuel Franco, lead author of a 2013 British Medical Journal report on Cuba based on national vital statistics. “We found high quality data on weight, disease and mortality that let us show very strong relationships.”

In the 1980s, thanks to Soviet agricultural support, most Cubans consumed 3,000 to 3,200 calories a day. However, when the Soviet Union collapsed in the early 1990s, Cuban farming struggled to fill the gap. In addition, gas was in such short supply that most public bus routes were eliminated.

Castro responded by declaring a special period (“periodo especial”) that included food rationing, the promotion of small-scale gardens and the distribution of more than 1 million Chinese-made bicycles.

The food shortage was severe enough that per-person calorie consumption dropped to about 2,400 calories a day in the 1990s, and typical adults lost about 10 pounds. At the same time, they had to exercise more by walking or riding bikes instead of taking buses. The number of Cubans meeting exercise guidelines climbed to an impressive 80 percent.

The combination of fewer calories and more exercise produced the outcome that health experts are constantly propounding. The obesity rate fell from 12 percent to 7 percent in 1995, and diabetes mortality dropped 13.95 percent per year from 1996 to 2002, a period when obesity rates remained low. During the same time frame, coronary heart disease mortality decreased by 6.48 percent per year.

After 2002, as Cuban agriculture began to respond and food imports picked up, obesity started climbing again. By 2010 it had reached 15.7 percent of the population. With this weight gain, the decline in diabetes reversed, and the disease’s mortality rate began increasing by 3.31 percent per year. The decline of heart-disease mortality dwindled to 1.4 percent per year.

“We had enough information through the years to show both the benefits of weight loss, and the harms of weight gain,” says Franco, who holds positions at the University of Alcallá outside Madrid and at Johns Hopkins University in Baltimore. “It was like giving the Cuban people a treatment, and then withdrawing the treatment. This makes us confident about cause and effect.”

When Franco and colleagues first noticed the improved Cuban mortality rates in the early 2000s, they figured something must be wrong with the data. After all, no other countries were losing weight and getting healthier. Franco flew to the Cuban Ministry of Public Health in Havana to take a firsthand look at the records. Not only were they accurate, but he also found additional, regional health statistics on diabetes. His skepticism turned to an appreciation for the consistent data.

Today, Cuban diet and exercise patterns mimic most of the rest of the world. There’s more cheap, processed food, and the buses are running again. “People remember the 1990s as a time of crisis,” Franco says. “They don’t want to live the way they did then.”

Yet he still believes the period carries an important message. “We showed that changes at the population level can have a very significant impact on mortality,” he says. “And that weight loss and weight loss maintenance require a combination of less food and more activity, especially transportation activity on foot and bikes. These are approaches that other countries should pursue rather than supporting private car use.”

More from Wellness:

Does eating fat make you fat? This doctor says no.

8 tweaks to make good-for-you foods even better

Prediabetes doesn’t have to be a ‘doomsday message’: What you need to know, and do