Fat distributed around the arms, legs and other parts of the body, which was found to be more prevalent in those of European descent, was less harmful, said lead researcher Scott Lear.

Dr Lear, an associate professor of kinesiology at Vancouver's Simon Fraser University, said the findings had far-reaching implications, since they suggested that Asians considered a healthy size by internationally accepted body measurement standards might in fact be dangerously overweight.

'If Chinese people get as fat or as big as Europeans, they'll actually experience a much greater risk for diabetes and heart disease,' he said. 'And that's a concern because obesity is increasing at a faster rate in China than it is in a lot of the western countries.'

The percentage of people who are obese in China remains lower than in most countries in the west. A national survey in 2002 found that 7 per cent of adults in China were obese. That compared with almost a quarter of adults in Canada who are obese, and more than half of US adults who are either obese or overweight.

However, China's rate of 7 per cent still translated to an estimated 60 million obese citizens. The number of adults who were overweight was even higher at 260 million, and health experts warned the country was rapidly catching up to the west in girth, as urbanisation, high-fat diets and sedentary lifestyles become increasingly common.

As the new study suggests, even more Chinese people could be at risk for weight-related illnesses than previously thought.

Although the research focused on participants living in Canada, there is no reason to believe the results would not apply in other parts of the world, Dr Lear said.

The study, published last month in The American Journal of Clinical Nutrition, used CT scans, or computerised tomography, to measure the amount of inner abdominal fat of participants. It found that Chinese subjects who weighted around 68kg carried 12 per cent more of the dangerous fat than European subjects who had the same total amount of body fat. At higher levels of total body fat, the Chinese group had up to 36 per cent more inner abdominal fat than their European counterparts.

Meanwhile, South Asian subjects of average weight had about 23 per cent more inner abdominal fat than similarly sized European participants.

Dr Lear said the results supported the need to redefine obesity in Asians.

Obesity is commonly diagnosed by measuring waist circumference and body mass index, or BMI, which is calculated from a person's weight and height.

Currently, regardless of ethnicity, a waist circumference of less than 102 centimetres for men and less than 88 centimetres for women is widely accepted as healthy. A BMI of between 18.5 and 25 is deemed normal, according to benchmarks used by the World Health Organisation and health experts around the globe.

In light of the recent findings, however, Dr Lear said those standard measurements should be lowered for Asians.

Asians should have a BMI of between 18.5 and 23, he said. Asian men should have a waist of less than 90 centimetres, and for women, that target should be trimmed to 80 centimetres or less.

Dr Lear said researchers do not know why body fat is distributed differently in people of different ethnic groups.

He and his colleagues analysed variables such as physical activity, diet, smoking, income and education, but found these factors did not affect the outcome of the results of their study. The varying body frame sizes of the participants had no effect on the results, either. One theory is that a history of recurring famines in Asia may have caused people to store excess fat in their bodies during times when food was abundant.

This 'thrifty genome theory' was developed in the 1960s to explain why certain ethnic groups were more susceptible to weight gain and diabetes.

Another possible explanation, called the 'genetic drift theory', is that certain genetic traits tend to be more prevalent in different ethnic populations based on mathematical probabilities, said William Gibson, assistant professor of medical genetics at the University of British Columbia.

Based on this theory, chance determines whether the majority of one generation inherits obesity-causing genes. Thus, over several generations, the probability of inheriting those genes will increase, Dr Gibson explained. 'Most scientists working in the field currently favour the thrifty gene hypothesis, but it's not completely proven,' he said.

Dr Lear plans to follow up on his study by re-examining participants in three years, and again in five years. The follow-ups would give researchers a better understanding of what happens to people's distribution of body fat as they gained or lost weight.

In the meantime, health experts maintain that lifestyle factors, such as diet and exercise, play a large role in controlling weight gain, but there appears to be little people can do to actually change where they gain or lose fat on their bodies.

Performing sit-ups, for example, won't likely help someone lose harmful inner abdominal fat exclusively, said Gwen Chapman, a professor of nutritional sciences at the University of British Columbia. 'That's more likely to affect the muscles, and so you might have more muscle tone in your stomach,' she said.

And while scientists have proved that high-fat and high-sugar diets lead to weight gain, they have yet to uncover whether culturally specific foods play a role in modifying people's risk of accumulating harmful fat, Dr Gibson said.