For centuries its produce has helped underpin a record of healthy hearts, giving Spain's northern region of Catalonia one of the lowest rates of heart attacks to be found anywhere in Europe.

But doctors meeting here for the World Congress of Cardiology warn that traditional Mediterranean-style diets - rich in vegetables, fruit, fish and olive oil but sparing in meat - are under siege from junk food.

Across Spain, as well as Italy and Greece, the story is the same, as young people increasingly turn away from old-style family meals in favour of burgers and fries.

"The Mediterranean diet is changing," Dr Ramon Estruch of the University of Barcelona told Reuters.

"Young people are not eating well today -- obesity is increasing and we are losing our diet. We need to return to the classical patterns of Mediterranean diet that we had in the 1960s and 1970s."

The virtues of eating fresh produce and olive oil were first recognised by medical researchers 50 years ago. Ever since, the scientific evidence has kept piling up.

Estruch and colleagues, for example, demonstrated two months ago that Mediterranean-style diets, rich in healthy fats, are even better than conventional low-fat diets at improving cholesterol, blood pressure and blood sugar levels.

DIETS CONVERGING

Yet doctors find that dietary patterns across Europe that were once very different are now converging - to the detriment of the cardiovascular health of those living on the Mediterranean rim.

"It's really a problem," said Dr Michal Tendera, president of the European Society of Cardiology (ESC).

"In northern Europe we are seeing a tendency to a more healthy diet," he added.

"Unfortunately, in those countries that traditionally have had a Mediterranean diet, the situation is not improving but deteriorating. Diet is getting worse and the amount of exercise that people take is very, very low."

Dr Valentin Fuster, president of the World Heart Federation, said economic development and a poor diet often went hand in hand, as people ate more and more of the wrong thing, while opting increasingly for fast food due to their busy lifestyles.

One in four Spaniards under the age of 19 are now overweight and between 16 and 17 percent are obese, he said.

The price is likely to be a rising toll of heart attacks and strokes, putting additional pressure on already strained public healthcare budgets.

In the Europe Union alone, the ESC estimates that cardiovascular disease costs the economy around 170 billion euros ($218 billion) a year -- 100 billion in healthcare provision and the rest in lost productivity.