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t_Articles
t_Articles
High levels of body fatness are related to an increased risk of diabetes,
coronary heart disease and certain cancers."
If you're sitting back complacently munching on an extra curry puff because
everyone says how slender you are, you may need to think again. New findings
suggest that more people in Asia may be fatter than previously believed. It
seems that the method of measuring overweight in the past may underestimate the
true prevalence of obesity in some Asian populations. Looking slender may not
correlate with the amount of body fat you carry.
The Body Mass
Index
Most studies use the body mass index or BMI (defined as body weight in kilograms
divided by height in metres squared) as an indicator for body fatness. The World
Health Organization of the United Nations has suggested that a BMI value of 25
be used as a cutoff point for overweight, while a BMI of more than 30 signals
obesity. These values relate to an increased morbidity and mortality in most
studies in Caucasian populations.
However, there appear to be differences in the relationship
between BMI and percentage body fat among ethnic groups. Some ethnic groups,
such as Asians and Africans, have a significantly higher percentage body fat for
the same BMI when compared to Caucasian populations. And it's the level of body
fat that poses problems for risk of chronic disease. Should we be using current
BMI standards for Asian populations?
Public
Health Implications
According to Dr Mabel Yap, Deputy Director of the Department of Nutrition,
Ministry of Health, Singapore, ethnic differences in BMI values have important
public health implications as they imply that cut-off points for obesity should
be lower or higher in different ethnic groups. "Lowering the cut-off point from
30 to 27 in Singapore, for example, would double the prevalence of obesity," she
said.
Dr Yap was involved in a pilot study with the School of
Physical Education of the National Institute of
Education, Singapore and Wageningen University, the
Netherlands, to test whether the differences in the relationship between BMI and
percentage body fatness amongst various ethnic groups are related to differences
in body build. Age and gender matched populations were studied in Singapore
Chinese, Beijing Chinese and Dutch Caucasians. In all, 120 individuals were
included in the study.
RELATIONSHIP OF BMI TO OVERWEIGHT AND OBESITY
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BMI Weight
Status
20-25 Normal
weight range
>25-30 Overweight
>30-40 Obesity
>40 Gross obesity
(WHO Expert Committee
on Physical Status, 1995)
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How to calculate
your Body Mass Index (BMI)
Your weight (kg)
¸ your height (m)2 = BMI
For example:
60 kg
¸ (1.65m x 1.65m) = 22.03 BMI
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Body Build
The participants' body build was determined by measuring sitting height (a
measure of relative leg length) and wrist and knee widths (to determine body
frame and skeletal mass). In addition, a slenderness index (height/ (sum of
wrist and knee width)) was calculated.
"Singaporean Chinese have the most slender body build.
However, for the same BMI, Singapore Chinese had the highest body fat levels
followed by Beijing Chinese and Dutch Caucasians," said Dr Yap. "The results
also show that body build is at least partly responsible for the differences
between ethnic groups."
Other studies in Thailand and Indonesia have produced similar
results. Both Thais and Indonesians have higher levels of body fat for a given
body mass index than either Caucasians or Chinese.
"It is not yet known if these differences correlate to
differences in levels of morbidity or mortality. However, the findings identify
a need for more detailed studies to confirm the results," said Dr Yap.
Editor's note: A paper on the above study is pending
publication in The International Journal of Obesity. The Impact of Body Build on
the Relationship Between Body Mass Index and Body Fat Percent. Deurenberg P.,
Yap M., Wang J., Lin F.P. and Schmidt G.
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