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Accurate body fat measure helps obesity battle

More accurate body fat measure helps in battle against obesity

The use of an alternative and more accurate method of measuring body fat in New Zealand children will help the fight against obesity say researchers from the Auckland University of Technology.

Director of AUT’s Body Composition and Metabolism Research Centre Associate Professor Elaine Rush, and AUT Masters student Kasalanaita Puniani were principal authors of a paper published in the November issue of the European Journal of Clinical Nutrition. The authors questioned the appropriateness of the commonly used body mass index (BMI) for measuring fatness in New Zealand children.

They suggest that bioimpedance analysis (BIA) is a more accurate method for establishing the likelihood of excess body fat in European, Maori and Pacific Island children. They will present their findings at the New Zealand Nutrition Society Conference, Too Little Too Much, in Dunedin on 6 and 7 November.

Children who are overweight or obese are more likely to become overweight or obese adults so it is important that an accurate measure be used for assessing the potential for obesity in children, says Kasalanaita Puniani.

“The prevalence of obesity in children throughout the world has increased significantly over the last 10 years and this has made the need for an accurate measure of obesity even more crucial,” she says.

In adults, BMI is widely used to define cut-off thresholds for them being overweight or obese and there has been much published on the relations between BMI and measures of body fat.

“These cut-off thresholds are based primarily on European data, but it is known from previous research that Maori and Pacific adults of the same body size as Europeans have higher fat-free mass (FFM) and lower fat mass, which makes the use of BMI to compare fatness among ethnic groups a doubtful classification.”

In children, the situation is more complicated as BMI is highly age-dependent and obesity is more difficult to define in the growing bodies of young people, she says. more

“For measurement or indexing of body fat, bioimpedance analysis (BIA) has clear advantages over BMI because it differentiates between fat and lean tissue whereas BMI does not.

“The bioelectrical impedance technique is a non-invasive, easily applied methodology for the measurement of body composition which has been accepted for field use by the international scientific community.”

The portability and ease of use of BIA instruments makes the technique very suitable for field use with the advantage of being less operator-dependent than approaches based on, for example skinfolds, which are often used for fatness measurements, says Associate Professor Rush.

The study involved a total of 172 children (83 male, 89 female) aged between five and 14 years of age. The ethnic composition of the sample was 55 European (26 male), 59 Maori (29 male) and 58 Pacific Island (28 male).

“The study confirms that in girls aged between 5 and 14 years, those of Maori and Pacific Island descent have a lower percentage of body fat than their European counterparts for the same BMI. We were not able to demonstrate a similar effect in boys. Our study suggests that these BMI thresholds need to be raised by three to four units for Maori and Pacific Island girls in this age range for valid comparison with New Zealand European children.”

BMI is not an appropriate measure of fat levels in a multiethnic population of European, Maori and Pacific Island girls but further study is required to establish for boys whether the relationship between BMI and body fatness is independent of ethnicity, says Kasalanaita Puniani.

“The robust equation to determine body fatness by bioimpedance analysis in New Zealand European, Maori and Pacific Island children in the 5 –14 year age range is more suitable than BMI for the determination of body fat levels as demonstrated by our study. As a more accurate measure of fat levels in New Zealand children it should prove a significant tool in the early detection of their potential to become obese adults.”


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