The danger in putting on weight isn't just a matter of "how much" but also "where" - and it seems some ethnic groups have a tendency to gain fat where it does the most damage.

People of Chinese and South Asian ancestry tend to have relatively more inner abdominal fat than people of European ancestry, which puts them at a higher risk of developing weight-related illnesses like heart disease, high blood pressure and diabetes, a Canadian study has found.

The results, published this month in the American Journal of Clinical Nutrition, show that current methods for measuring body fat may not be accurate for people who are not of European descent because the targets generally used for waist circumference or body mass index (BMI) are based on studies whose participants were predominately of Caucasian European origin, said Dr Scott Lear, the lead researcher from the School of Kinesiology at Simon Fraser University in Burnaby, British Columbia.

This inaccuracy could make it harder to identify weight-related problems and treat people in certain ethnic populations, even when they are the same size as Europeans. "If we use targets based on Caucasians for the Asian population, we're not going to identify people until they're at a higher risk," Lear said. The study looked at 800 healthy Chinese, South Asian, Aboriginal and European participants, evenly distributed among the four ethnic groups.

The participants' amounts of abdominal fat were compared for the same amount of total body fat, Lear said, because in a random sample, the Chinese and South Asians would tend to be smaller than the Europeans and would have less overall body fat even at the same body mass index (BMI) or body fat percentage.

Inner abdominal fat, or visceral fat, is not the fat you grab when you pinch an inch on your stomach. Instead, it sits behind the abdominal muscle wall around the organs, and tends to be more strongly associated with heart disease and diabetes.

The researchers found that Aboriginals didn't show any difference in their body fat distribution when compared to Europeans, but the Chinese and South Asian participants tended to have a greater proportion of their body fat in the inner abdominal region.