Muesli, Skiing and Health: Why Swedes Stay Slim

WITHIN EUROPE, Sweden ranks as the slimmest nation, thanks to muesli, skiing and a belief in physical prowess - reflected in the popularity of its sports clubs, which boast among the highest membership in Europe. In Germany, sausages and Sachertorte combined with a commitment to Vorsprung durch Technik has made the most prosperous nation also the weightiest.

In China, a largely rural lifestyle which makes heavy physical demands combined with a low-fat, rice-based diet keeps the population trim. In the US, where people commute to offices in air-conditioned cars and only break sweat when the pizza delivery is late, average seat sizes have increased.

Cultural factors play their part. In Samoa and neighbouring islands in the Pacific, obesity has long been regarded as a symbol of high status and prosperity and is seen as attractive as a result. In recent years, there have been signs that these traditional notions are changing as more Westernised ideas of an attractive body size take hold.

There are also sex differences. Women to be fatter than men, a legacy of child-bearing. But here, too, culture plays a part. In the United Arab Emirates, male obesity rates are similar to those in Britain but among women they are more than twice as high

Despite the enormous international range in rates of obesity, only about 20 per cent of differences in body shape can be attributed to genes, according to Professor Garrow.

"If it were the case that the Chinese and Japanese had something in their genes that kept them thin they wouldn't become taller and fatter when they migrated to the US. But migration studies show that they do.

JEREMY LAURANCE