Body Mass Index (BMI), the standard measure of
obesity, is badly flawed and a more accurate gauge
should be developed, according to doctors.
Writing in Friday's Lancet medical journal, the
researchers from the Mayo Clinic College of Medicine,
Rochester, Minnesota, found that patients with
a low BMI had a higher risk of death from heart
disease than those with normal BMI.
At the same time overweight patients had better
survival rates and fewer heart problems than those
with a normal BMI.
This apparently perverse result, drawn from data
from 40 studies covering 250,000 people with heart
disease, did not suggest that obesity was not
a health threat but rather that the 100-year-old
BMI test was too blunt an instrument to be trusted.
"Rather than proving that obesity is harmless,
our data suggests that alternative methods might
be needed to better characterize individuals who
truly have excess body fat compared with those
in whom BMI is raised because of preserved muscle
mass," said lead researcher Francisco Lopez-Jiminez.
About 30,000 people in Britain die due to obesity
every year and 300,000 in the United States where
the condition is now thought to have overtaken
smoking as the main cause of preventable death.
Body Mass Index, invented by Belgian polymath
Adolphe Quetelet between 1830 and 1850, is a measure
of body fat calculated from height and weight.
A figure of less than 18.5 is considered underweight,
while from 18.5 to 24.9 is normal, 25 to 29.9
is overweight and anything over 30 is categorized
as obese.
Intended as a broad indicator of general health,
it has become a standard diagnostic tool of heart
disease risk.
Maria Grazia Franzosi from the Instituto Mario
Negri in Milan, writing in the same issue of the
Lancet, noted that a 52-country study comparing
four different tests -- BMI, waist-to-hip ratio,
waist measure and hip measure -- found that waist-to-hip
was the best predictor of heart attack risk.
"BMI can definitely be left aside as a clinical
and epidemiological measure of cardiovascular
risk," she said.
"Uncertainty about the best index of obesity
should not translate into uncertainty about the
need for prevention policy against excess bodyweight,"
she cautioned.
About Body Mass Index
(BMI)
The
Body Mass Index is a poor measurement and
a controversially inaccurate indicator to assess
health. An ideal BMI (which the measurement considers
to be healthy) is between 20.5 and 21.5. However,
it makes absolutely no distinction between body
weight from muscle and body weight from fat which
labels a broad segment of the athletic and similar
healthy populations as overweight and obese. It
is limited in its ability to predict deaths caused
by heart attacks or strokes (yet it's still used
by Physicians). High BMIs (35 and over) are linked
to increased risk of cardiovascular events but
not to increased mortality overall. BMIs less
than 20 are linked to increased risk of cardiovascular
events AND to total mortality.
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