The Mediterranean diet has been reported to increase longevity, protect against heart disease and may even lower the risk of some cancers.
But some nutritionists have raised concerns that this kind of regime, rich in olive oil and other unsaturated fats, could lead to overweight and obesity.
Researchers from the University of Athens gave around 23,600 participants in the Greek European Prospective Investigation into Cancer and Nutrition Study a validated food-frequency questionnaire to assess whether they followed the traditional Mediterranean diet.
They also recorded anthropometric, sociodemographic, physical activity, and other lifestyle characteristics.
Writing in this month's issue of the American Journal of Clinical Nutrition (vol 82, no 5, pp935-940), they said that following a Mediterranean diet was essentially unrelated to body mass index (BMI), a measure of overweight.
This counters some theories that had attributed the high obesity rates in Greece and Italy, both on the Mediterranean, with the traditional diet.
"Overweight is a genuine problem in Greece and perhaps other Mediterranean countries, but it is likely to be related to limited physical activity in conjunction with excessive positive energy balance, brought about by the westernization of the Mediterranean diet," concluded the researchers.