FFA Issue 21 - July 2004 -
Healthy Weight Advice – One Size Doesn’t Fit All!
t_Articles
Healthy Weight Advice – One Size Doesn’t Fit All!
Health experts are
concerned because the number of people classified as overweight or obese
is rising all over the world, and the evidence is clear that those who
are successful in controlling their total body fat, are much less
likely to experience premature chronic degenerative diseases such as
heart disease, stroke, high blood pressure, diabetes and high blood
lipids. However, experts are beginning to understand that the
relationship between body weight and the likelihood of developing
chronic degenerative diseases is more complicated than a simple
overweight = increased risk formula.
For those
individuals who are interested in exactly how body weight in relation to
health status can be assessed and how to recognize when to take action,
here is a summary of some of the latest scientific thinking and some
practical tips for action. However, generalised advice can never be a
substitute for personalised medical review and treatment, and those
readers with any serious health concerns are strongly advised to consult
a qualified medical practitioner.
The Asia Phenomenon
The risk of
developing chronic ill-health appears to increase amongst many Asian
populations at lower levels of body weight, than in Caucasian
populations. Experts have identified some physical characteristics
which are relatively common in Asian populations, and which are
contributing to this phenomenon. In particular, adults with excess fat
concentrated around the abdominal area, and/or who were under-nourished
in very early life and subsequently gained excess body fat very rapidly
as infants (the so-called 'Barker effect') and/or who lead very
sedentary lives seem to be much more likely to suffer from ill health
and disease associated with overweight and obesity. (1)
Vital Statistics
Here are some
recommended methods for assessing individual health status, using
individual vital statistics and some simple mathematics:
BMI
The global standard
for classification of body weight as normal, underweight, overweight or
obese is Body Mass Index (BMI). BMI is calculated by dividing a person's
weight in kilograms by their height in metres squared. Until recently,
the same classification standards have been used in all parts of the
world, to assess and categorise body weight: A BMI of 18.5 to 25 is
traditionally classified as normal, 25 to 30 as overweight and is
associated with increased risk of developing weight-related disorders,
and above 30 is classified as obese and at high risk of developing
weight-related illness.
In recent years,
experts, have observed that weight-related disorders are more common in
some Asians ethnic groups at BMI levels above 23. An expert group of the
WHO has therefore recommended a lower BMI scale for Asians: 18.5-23 for
increasing but relatively low risk of developing weight- related
ill-health; 23-27.5 for increased risk; and 27.5 or more signals high
risk. (2)
A disadvantage of
the BMI scale however, is that it may overestimate body fat in athletes
and others, such as Pacific Island ethnic groups, who have a muscular
build. BMI may also underestimate body fat in older persons and others
who have lost muscle mass. Hence, experts recommend the use of BMI
combined with waist circumference or/and waist-to-hip ratio for a more
accurate assessment (3).
BMI Formula
= Weight in Kilograms
(Height in
Meters) x (Height in Meters)
Waist Circumference
Waist circumference
is measured around the narrowest point between ribs and hips when viewed
from the front after exhaling. Waist circumference, is a measure of
abdominal fat and a good indicator of health status, even when the BMI
calculation falls within the range classified as normal. Waist
measurements of over 102 cm (40 inches) in men and over 88 cm (35
inches) in women were set as the global thresholds for determining
increased likelihood of developing weight-related disorders.
More recently, lower
thresholds for waist circumference have been recommended for Asian
populations. The Working Group on Obesity in China organized a review of
the data on the relationship between BMI, waist circumference and risk
factors of related chronic diseases. Based on this review of all the
evidence collected to date, the Working Group recommended waist
circumferences of over 85 cm for men and over 80 cm for women in China,
as the threshold figures for diagnosis of central or abdominal obesity
(4). These figures have not been recommended for the whole of Asia but
nevertheless, do provide an alternative scale to the global figures
which may not fully take into account the differences in fat
distribution and body composition between Caucasian and Asians.
Waist-to-Hip Ratio (WHR)
Waist-to-hip ratio (WHR)
is the ratio of a person's waist circumference to hip circumference.
This measurement can be calculated by dividing waist circumference by
hip circumference.
WHR, like waist
circumference is a tool to assess distribution of body fat. For most
people, and perhaps especially Asian populations, abdominal fat causes
more health problems than carrying extra weight around their hips or
thighs. A WHR of 0.90 or less is considered healthy for men and a ratio
of 0.80 or less is considered a sign of good health for women. A waist :
hip ratio of 1 or higher signals increased risk of ill health and an
indicator that action to shed some body fat from the tummy would be wise
(2).
Signals for Action
Together, these
three measures of body size, provide some very useful criteria against
which to assess body weight and determine action targets, to maintain,
lose weight or recognize and halt gradual weight gain. It seems for
Asians in particular; an assessment not just of body weight, but also
abdominal fatness is a wise and relatively simple health check.
Regardless of
whether individual targets are to maintain weight or lose weight, the
guidelines to maximize individual chances for a long and healthy life
are the same: Aim to gradually establish a healthful lifestyle which
fits in with other commitments of daily life, and is based on a low-fat,
varied and balanced diet, combined with regular physical activity. The
yo-yo effect of repeated weight loss and weight gain, which occurs in
those who follow a repeated pattern of dieting to lose weight rapidly,
but then gradually regain the weight lost when they return to old eating
habits, brings its own health risks and makes long term weight control
increasingly more difficult.
Thirty to sixty
minutes every day of moderate to vigorous physical activity such as
brisk walking, or swimming, helps in weight maintenance and weight loss,
and regardless of body weight, massively reduces individual risk of
developing heart disease, strokes and other chronic disease because of
the benefits it brings to cardiovascular health. An additional incentive
to exercise may come from a study reported in the Journal of the
American Medical Association which found that regular exercise reduced
"intra-abdominal" fat, and therefore trimmed waistlines even in those
who lost no weight (4). Regular exercise also brings many other
benefits, such as improved sleep quality and psychological well being.
Experts also stress
that maintaining a healthy weight needs to be a lifetime goal. The World
Health Organisation recommends that adults should aim to gain no more
than 5 kilogrammes throughout adult life. The first steps towards this
goal could be to invest in some simple weight scales, a tape measure and
perhaps a calculator - the only equipment needed for individuals to
establish lifelong oversight of healthful body weight.
References:
1. Barker D.,1998. Mothers,
Babies and Diseases in Later Life. Churchill-Livingstone, London
2. Appropriate
body-mass index for Asian populations and its implications for policy
and intervention strategies WHO expert consultation. Lancet 2004;
363:157-63.
3. Use of body mass
index and waist circumference to predict risk of chronic disease.
Journal of the American Dietetic Association, June, 2001.
4. Zhou Bei-Fan1 and
the Cooperative Meta-analysis Group of Working Group on Obesity in
China. Predictive values of body mass index and waist circumference for
risk factors of certain related diseases in Chinese adults: study on
optimal cut-off points of body mass index and waist circumference in
Chinese adults. Asia Pacific Journal of Clinical Nutrition. Volume 11
Issue s8 Page S685 - December 2002.
5. ML. Irwin, Y.
Yasui, CM. Ulrich, et al., Effect of exercise on total and
intra-abdominal body fat in postmenopausal women. JAMA, 2003, vol. 289,
pp. 323330.
