Disease indicator fails Asian New Zealanders
17 December 2004
Lifestyle disease indicator fails Asian New Zealanders
A new study suggests the traditional method for measuring obesity is failing some Asian New Zealanders who are likely to develop obesity related diseases but are not being identified as high risk.
The study, which will be published tomorrow in the New Zealand Medical Journal by a team of researchers led by Auckland University of Technology’s Associate Professor Elaine Rush, surveyed a total of 114 healthy men (64 European, 31 Pacific Island, 19 Asian Indian) aged 17–30 years.
The subjects underwent measurements of height, weight, and body composition by total and regional body dual-energy X-ray absorptiometry (DXA). Percent body fat, fat-free mass, bone mineral content, bone mineral density, abdominal fat, thigh fat, and appendicular skeletal muscle mass were obtained from the DXA scans. This direct assessment of body fatness composition was compared with the Body Mass Index (BMI), which is the most widely accepted method for assessing levels of body fat, risk for disease and is sanctioned by the World Health Organisation (WHO).
The WHO classifies BMI readings into categories that indicate whether someone is healthy, overweight or obese. The cut-off point for its classification of obesity is a BMI of more than 30 kg/m2, which is intended as an internationally useful threshold for reflecting Type 2 diabetes risk and cardiovascular diseases.
“Based on this cut-off, our research shows that Asians from the Indian subcontinent have low rates of obesity yet, relative to Europeans it is known from other studies that they have a higher prevalence of coronary heart disease and Type 2 diabetes.
“It is widely recognised that obesity and obesity related diseases are an increasing global problem now at epidemic proportions. The body mass index is commonly used as a surrogate measure for obesity because of its ease of measurement and is widely accepted by health professionals,” says Associate Professor Rush.
When the researchers compared data across the three ethnic groups, Pacific Island people had more muscle and less fat than Indians with the same BMI.
“The relationship between percent body fat and BMI is different for European, Pacific Island, and Asian Indian men which may, at least in part, be due to differences in muscularity. Asian Indians have more abdominal fat deposition than their European and Pacific Island counterparts. The use of universal BMI cut-off points are not appropriate for comparison of obesity prevalence among these ethnic groups.”
Associate Professor Rush says an increasing prevalence of obesity related diseases in Indian New Zealanders is a likely result of their higher levels of percentage body fat over time.
“Lean muscle mass determines fitness – because Indian New Zealanders are less muscular and carry more abdominal fat, they can be considered a high risk group for diseases like Type 2 diabetes and coronary heart disease.”