BMI is a commonly used measure of obesity but it has limitations because it does not distinguish between fat, muscle and bone mass. While BMI can provide a general indication of health risks, it may miscategorize athletes and older individuals. Alternative measures like waist circumference and body composition tests using bioelectrical impedance provide a more accurate assessment of obesity risks by measuring abdominal fat distribution and actual body fat percentage. Experts recommend using a combination of measures like BMI, waist circumference, and other health factors to evaluate weight-related health risks.

1. What's Wrong With BMI
By Dr. Sanjay Gupta
Is body mass index the best measure of the
obesity problem, and what other options are
there?
One out of three American adults is obese, and
childhood obesity has more than doubled in the
past 30 years. It’s an epidemic with very serious
health risks, from heart disease to diabetes to
cancer. It’s also taking an incredible financial toll:
Studies have put the national healthcare cost of
obesity at over $190 billion a year.
Behind these staggering figures are measurement
tools that the medical community uses to
determine who is at risk. One of the most common
is body mass index (BMI). The problem is that BMI
alone doesn’t tell the whole story.
BMI is a mathematical equation — weight (in
pounds) divided by height (in inches) squared,
multiplied by 703 — to calculate an individual’s
body fat. An adult with a BMI of 30 or higher, for
instance, is considered obese. But because BMI is
based on body weight rather than body

2. composition, it doesn’t take into account how
much of that weight is from muscle, bone or water
as opposed to fat.
“BMI is a useful number in general terms, but it
doesn’t tell us where the fat is distributed or
distinguish between fat and muscle,” said
Subhashini Ayloo, MD, a bariatric surgeon at
University of Illinois Hospital. That means an
athlete who has more muscle mass and strong
bones could have a high BMI that would categorize
them as overweight or even obese. On the other
hand, older people who have lost muscle may
have a deceptively lower BMI.
While the Centers for DiseaseControl and
Prevention considers BMI “a reasonable indicator
of body fat,” it doesn’t recommend it as a
diagnostic tool.
“It’s not perfect but it’s definitely a useful tool,”
said Ellen Demerath, an associate professor of
epidemiology and community health at the
University of Minnesota. “It should be the first
step in measuring an individual’s health
assessment, but other tests can also be useful.”

3. One simple alternative to BMI is measuring waist
circumference which, as Demerath points out,
“can be an indicator of risk for many obesity-
related diseases.”
Men with a waist circumference of more than 40
inches and women with a circumference of more
than 35 inches are at a higher risk for developing
obesity-related conditions like type 2 diabetes,
high blood pressure and high cholesterol. In a new
study out this month, so-called “apple-shaped”
people who carry more fat around their bellies are
also at a higher risk for kidney disease.
“If someone has a pear shape and their weight is
in the hips and thighs, which is classically a female
body shape, they don’t have the same risk
factors,” said Eric Westman, MD, an internist at
Duke Health Center in Durham, N.C.
Another method of measuring fat that’s becoming
more popular and accessible is bioelectrical
impedance — a device resembling an ordinary
scale that measures body composition by sending
a low electrical current from footpad electrodes.
“It’s a more accurate way of measuring the actual
percentage of fat,” Dr. Westman said. “You see

4. them a lot now in health clubs, and they’re
available for home use.”
BMI is still a valid and inexpensive screening tool.
But it’s just one piece of the puzzle. The National
Heart, Lung, and Blood Institute recommends that
any weight-related health assessments shouldbe
based on a combination of BMI, waist
circumference and other individual risk factors
such as high blood pressure, cholesterol or
physical inactivity.
“The guidelines for determining obesity are not
hard and fast rules, they’re a consensus that most
doctors agree on,” Dr. Ayloo said. “Right now one
of the criteria used is BMI because it’s easily
accessible, but it’s not perfect on its own.”