The Kaiser Permanente Study, which appears in the International Journal of Epidemiology, makes sober reading for a country that, more than any other, has placed gastronomy and good food at the heart of its national identity.
But a fast food culture that is quickly taking over more traditional patterns of consumption is changing the character not only of city centres and family meals, but also the countrys health profile.
An estimated 50 million Americans have metabolic syndrome, a combination of conditions, including abdominal obesity, high triglycerides, low HDL cholesterol, elevated blood pressure, and insulin resistance.
Now the French may be headed for similar problems.
The new study, led by an American researcher working with scientists at France's Institute National de la Sant et de la Recherche Mdicale (INSERM), followed a normal-weight group of 3,770 French men and women for six years.
They found that each kilogramme of weight gain increased the risk of the metabolic syndrome by 22 per cent. After six years, 21 per cent who gained nine kilograms or more (19.8 pounds or more) developed the syndrome.
Teresa Hillier, lead author of the article, said that it is important to note that the more pounds normal-weight people gain, the more their risk increases for developing the metabolic syndrome. Secondly, insulin levels had the greatest proportional increase among all metabolic syndrome parameters across all weight-change groups, nearly doubling for both men and women.
"This is important new information because it shows that even mild weight gain is associated with insulin resistance," she said.
For France, which has had the lowest prevalence of obesity among nine northern European countries and among the lowest of westernised countries in the world, these results raise some important social and cultural questions.
The so-called French paradox - the belief that there is something in the French lifestyle that protects them against obesity, heart disease, and diabetes - may be a myth or it may be a truism that is passing into history.
Because as more and more French men and women adopt a lifestyle that is increasingly American - fast foods, processed foods, soft drinks and little or no exercise - they may be entering the front end of the obesity and diabetes epidemics that began in America nearly 20 years ago.
Europe is beginning to take notice. Speaking at a conference on metabolic syndrome in Athens last year, professor Philip James, chairman of the London-based International Obesity TaskForce, said that governments needed to take action to slow the rise in this condition in Europe.
Epidemiological evidence suggests that consumption of wholegrains and following a typical Mediterranean diet may reduce the risk of this condition. Other studies have investigated benefits from specific nutrients that can improve blood sugar control, such as chromium supplements and antioxidants.
France recently banned all vending machines from schools in an attempt to tackle the problem. But the Kaiser Permanente study underlines the fact that more action is needed if an American-style epidemic is to be avoided.
The European Commission says that 14 million Europeans are obese or overweight, of which more than 3 million are children. Obesity-related illnesses, which include heart disease and diabetes, account for up to 7 per cent of healthcare costs in the Union.
The Kaiser Permanente study was funded by a Trans-Atlantic Fellowship and awarded to Hillier by the American Diabetes Association-European Association for the Study of Diabetes (ADA-EASD). Dr. Hillier spent a year (2004-2005) in Paris at INSERM working on this study and other projects.
Kaiser Permanente is one of America's leading integrated health plans. It is a non-profit group that serves the health care needs of 8.3 million members in the US.