A sight that assaults visitors to certain parts of the Western world - the United States, Britain and Australia in particular - is widespread obesity. Fatness - let's call it what it is - is an epidemic.

Hong Kong, however, has remarkably few corpulent individuals. But the number of overweight people, both here and on the mainland, is rising due to increased affluence and rapidly changing dietary habits.

At one time, brightly coloured advertisements for medicines and infant formula featured Chinese babies that were - by modern standards - very fat. In a country where catastrophic famine occurred regularly, images of plenty were what everyone wanted to see. Who wanted scrawny offspring if they could have "healthy", porky ones instead?

But times have changed. Seriously overweight children can be seen all over the mainland. Part of the problem, it has been alleged, is the one-child policy, introduced in 1979. As with most forms of well-intentioned social engineering, the Frankenstein's monster effect was not anticipated, and the programme has spawned a generation of selfish, overindulged "little emperors".

In Hong Kong, the battle against the bulge has resulted in numerous so-called solutions. Loose consumer-protection regulation means advertisers can tout dubious benefits of products and services. We've seen advertisements for body-toning salons where - for a price - one can be plugged into a variety of electrical gadgets, lay on a couch and - with no further effort - get a rippling six pack in weeks. Yeah, right.

Physical exercise undertaken for its own sake was not widespread in traditional China. Recreational activities for the tiny fraction of the population who had regular leisure time were mostly sedentary pastimes. Calligraphy, flying kites, writing poems - none of these pursuits raises a sweat. And those who worked manually for a living were often too tired for further activity; rest time was reserved for sleep.

Missionary influence from the mid-19th century - also behind many other aspects of societal change in China, from attitudes to women and foot-binding to notions of democracy and liberty - helped introduce a widespread exercise culture.

Mission schools encouraged sports and other physical activities as part of the Enlightenment-influenced mens sana in corpore sano ("healthy mind in a healthy body") approach to education. An inevitable - if rather unfair - extrapolation maintained that China was an easy target for foreign intervention because the Chinese education system did not emphasise sports, and therefore encouraged an effete culture. With unthinking irony, missionaries ignored the fact they were in the country in the first place as a direct result of foreign aggression.

Attitudes gradually changed and by the 1920s, mission school influences had expanded into missionary-funded universities and a widespread YMCA/YWCA movement. In the early 30s, this evolved into the Nationalist government's New Life Movement. Calisthenics, anti-spitting slogans and various other health-promoting notions were combined into a nationwide regeneration movement. This campaign was an initiative of Madame Chiang Kai-shek, an Americanised Methodist advocate of "muscular Christianity". After the Communist takeover, the new rulers followed most of its tenets - but without referring to the earlier versions.