Professor John Komlos, of the University of Munich, analysed data from the last 200 years for around 250,000 people.

He found that while Europeans are getting increasingly taller, Americans have "stopped growing."

In the 1800s, the Dutch were, on average, three inches shorter than Americans - now they are around three inches taller.

It could be linked to factors such as the better medical attention available in western and northern European countries

Professor John Komlos, University of Munich

He discovered that, at the time of the American War of Independence in 1775, the average American man was 5ft 9 - about two inches taller than the average British man.

Now, the tables have been turned - with the British around half an inch taller than the Americans, who have now reached an average height of 5ft 10.

But Dutch men have an even bigger height advantage over the Americans - they reach an average of 6ft 1.

Immigrants, and people of either Hispanic or Asian ancestry were not included in the study.

'Baby care crucial'

Professor Komlos said the importance of the increase in obesity has been recognised, but less attention has been paid to what height can tell scientists about a nation's health.

George Bush and Tony Blair demonstrate the height difference

He said the Dutch advantage was probably due to providing the "world's best" pre and post-natal care.

In contrast, around 40 million Americans have no health insurance.

Professor Komlos told BBC News Online: "The reasons behind this height difference are a big mystery."

But he said it was likely there were social, economic and medical differences between Europe and America.

"We think it could be linked to factors such as the better medical attention available in western and northern European countries, and better access to a welfare state.

"There is also a more even distribution of income in western and northern Europe."

Right foods?

Writing in the Economics and Human Biology, Professor Komlos added: "There is much concern about the obesity epidemic in the US, because of health consequences, but the fact that the physical stature of Americans has been lagging well behind European levels has all but eluded comment.

"Within half a century a veritable metamorphosis in the shape of the American population took place without notice; from being the tallest in the world still around World War II, Americans have become one of the most obese at the start of the 21st century."

Amanda Wynne, of the British Dietetic Association, said: "Many things will influence height - including genetics - but nutrition is an important factor.

"The US has very good access to food, they are not deprived of nutrition. But if they are eating the right foods is another question.

"Good nutrition is very important for overall wellbeing."