The figures showed that 16.8 per cent of girls and 22.5 per cent of boys were overweight in 2006, compared to only 8.9 per cent and 11.3 per cent, respectively, in 1993.

According to paediatrician Alfred Tam Yat-cheung, a change in lifestyle is the biggest reason for the rising obesity rates among children.

Today's youngsters eat more snacks, play computer games and don't do enough exercise, he said.

Stanley Hui Sai-chuen, associate professor at CUHK's sports science department, said childhood obesity is often linked to cardiovascular diseases and diabetes. Obese children also tend to remain overweight when they grow up, he added.

Sadly, health problems are not the only obstacles that overweight children have to face.

Tsang Chi-kin, who packs 104 kilograms on a 1.75-metre frame, said he is frequently harassed in school.

'I've been called fei chai and chu pa Kin [fat boy and pork chop Kin in Cantonese] ever since I was young,' said the 16-year-old.

'It upset me a lot at the beginning, but now I am used to it.'

While overweight boys are called various names, girls face other kinds of social pressure.

The slimming craze that has gripped the city is one of them.

About one out of five posters displayed on the MTR features an ultra-thin model in a bikini.

Such advertisements lead young girls to think that being slim is beautiful.

As this trend catches on, clothing sizes are getting smaller and smaller.

A 'large' size today could have been a 'medium' a few years back.

Obese teenagers have a tough time shopping for clothes.

'I don't have much choice when I go shopping. Even if I lost 20 pounds, the largest size wouldn't fit,' said Cathy Wang Tze-wai, 15, who is 1.48m tall and weighs 68kg.

'This pressure for girls to be slim is driving me insane. Why are tall, slender girls better than heavier ones?'

Obese youth say they are unable to make as many friends as their slimmer peers.

They are also regarded as less clever, and blamed for taking more than one seat on public transport.

A recent survey by the University of Hong Kong (HKU) found that the bigger babies are when they are born, the faster they will grow in the first three months. This means they have a higher chance of being overweight or obese when they are seven years old.

Researchers still cannot pinpoint the reasons behind this phenomenon.

'We are still trying to figure out if it is related to genetics. Yet there's been similar observations in western countries, so that means this is not something abnormal,' said Mary Schooling, research assistant professor at the department of community medicine at HKU.

'We found that breast-feeding children in their first six months could help reduce obesity. But if they start to gain weight at a later stage, exercise and a balanced diet are the keys to slimming down. There's no magic solution [to fighting obesity].'