Research queries ethnic fairness of obesity index

By REBECCA WALSH

Auckland researchers have questioned the use of the body mass index to compare fat levels among Maori, Pacific and European children in New Zealand.

Associate professor Elaine Rush, director of the Auckland University of Technology's Body Composition and Metabolism Research Centre, said the body mass index used a person's height and weight but it did not measure what was inside a person's skin, for example fat or muscle.

Research she had completed with AUT Masters student Kasalanaita Puniani indicated a more accurate way of measuring body fat and a child's likelihood of becoming obese was a bioimpedance analysis (BIA).

The test involved measuring the amount of water in a person's body and his or her electrical resistance - "the more fat you have the less well you conduct electricity".

Researchers could then work out the percentage of body fat.

Dr Rush's study of 172 children, aged 5-14, found that Maori and Pacific Island girls for the same BMI had a lower percentage of body fat than their European counterparts. The same was not true for boys.

Earlier research had already found Maori and Pacific adults of the same body size as Europeans had more muscle and less fat.

Dr Rush said it was possible that figures for obesity rates among Maori and Pacific could have been overstated depending on the cutoff points used. She wanted to see the BIA test used to help determine which children were at risk of becoming obese.


NZ Food, NZ Children: Findings of the 2002 National Children's Nutrition Survey