Body Fat Measurement: Percentage Vs. Body Mass
What's the best measurement to assess health risks from being overweight? Experts say BMI and body-fat percentage both have their place.
Weight, body fat, body mass index -- what do all
these numbers mean? And what do they really tell you about your health?
Some experts tout BMI, or body mass index, as the most accurate
way to determine the effect of weight on your health. In fact, most recent
medical research uses BMI as an indicator of someone's health status and
The CDC provides the following ranges for BMI values for
|Underweight Less than 18.5
Recommended 18.6 to 24.9
25.0 to 29.9
But others feel that body-fat percentage is really the way to
"The BMI numbers are way too general to be really
useful," says Tammy Callahan, marketing manager of Life Measurement Inc.,
which manufactures a fat analyzer for use in gymnasiums and medical settings.
"These numbers were developed using data from enormous numbers of people.
They don't tell you anything about your own body composition, how much of your
weight is fat, and how much is muscles and tissue."
But don't throw out that BMI chart just yet.
Are You At Risk?
"I'm not against people using devices to figure out fat
percentages, but it is a well established fact that your BMI number does tell
you a lot about your risk of diseases, especially heart disease and diabetes," says Harry DuVal,
PhD, associate professor of exercise science at the University
of Georgia in Athens. "Fat percentages just don't have enough research
behind them yet to tell you how much risk of disease you face."
You're probably familiar with body mass index. BMI is an
equation that gives you a numerical rating of your health based on height and
weight. As your BMI goes up, so does your risk of developing weight-related
diseases, such as heart disease and diabetes. (To figure your BMI, use our calculator.)
But even as more and more people are using their BMI number as
an indicator of overall health, research on fat percentage is improving.
In September 2000, the American Journal of Clinical
Nutrition published a study showing that body-fat percentage may be a
better measure of your risk of weight-related diseases than BMI. Steven
Heymsfield, MD, director of the Obesity Research Center at St. Luke's Roosevelt
Hospital in New York, and his colleagues evaluated more than 1,600 people from
diverse ethnic backgrounds. Researchers took body-fat measurements and studied
how their body fat related to disease risk.
"Many studies have related BMI to disease risk," noted
Heymsfield. "What we did was correlate body-fat percentage to BMI, allowing
us to take the first big step toward linking body-fat percentage to disease
risk. This new research reveals the value of assessing body fat more directly
using the latest scientific technology to measure body-fat percentage," he