The standard method of measuring obesity may fail to pick up health problems in Asians, an international conference heard Thursday.

The body-mass index defines obesity based on the relationship between weight and height.

World Health Organization guidelines say a BMI of more than 25 kilograms per metre squared is overweight, and more than 30 kilograms per metre squared is obese.

But East and South Asians have shown weight-related health problems at a lower cut-off than Caucasians, researchers have found.

Chinese, Japanese, Koreans and Indians show hypertension and diabetes at a lower BMI threshold of 23, Pan Wen-Harn from the Institute of Biomedical Sciences in Taiwan told the 10th International Congress on Obesity in Sydney, Australia.

Conference participants are discussing whether to formally change the WHO guidelines to include ethnic-specific criteria.

The waist-to-hip ratio is considered the best measure of obesity, but it is less practical, Wen-Harn said. 

In India, genetic factors are mainly to blame for high rates of hypertension and diabetes, said Naval Vikram of the All India Institute of Medical Sciences, New Delhi. The westernization of the Indian diet and less physical activity also contribute to the metabolic disorders, Vikram said.

Indians tend to have a greater proportion of body fat than Caucasians, Statistics Canada noted in a 2005 report on the health of immigrants.

Indians also tend to have a low body-mass index, high abdominal fat and low waist circumference, Vikram said.

The number of diabetics in India, China, Pakistan and Japan could reach 120 million by 2010, WHO data suggest.