BMI And Waist
Circumference Risk Assessment
Chester J. Zelasko, Ph.D. |
March 29, 2005
Think about this:
you have a friend who is very overweight. You just know that he’s going to
have a heart attack if he tries to climb a flight of stairs. Then your other
friend, who doesn’t look overweight and seems to be in good shape, keels
over with a heart attack. It doesn’t make any sense, does it? But it happens
every day. It doesn’t mean that excess body weight is not a factor in the
development of disease--it most assuredly is--but assessing the risk for
developing a disease is complicated. This is especially true when it comes
to non-invasive measures, including anthropometric measurements such as body
weight. But recent research has developed a more precise way of assessing
such risk, and that’s the topic of this Newsletter.
The Body Mass Index (BMI) uses height and weight to calculate the surface
area of a human being: the more surface area you have, the more body fat you
have, with the exception of those who are very muscular--professional
football players, for instance. (Click
here to determine your BMI.) BMI can tell you whether you’re normal
weight, overweight, or obese. What it cannot do is predict whether you’re at
greater or lesser risk for heart disease or diabetes because there are other
factors to consider. One of those factors is visceral adiposity or the fat
around your waist.
Researchers have discovered that the Waist Circumference (WC) is a much
better predictor for determining who is at risk for heart disease and
diabetes than BMI (1). If you have a tendency to store fat around your
waist, the risk for heart disease and diabetes increases.
The measurement is simple. Using a flexible tape (a measuring tape is
included with every 30 Day Plan), measure your waist at the widest
point, usually an inch above or below the umbilicus (belly button). It
should just cover your skin without making indentations. Don’t suck your gut
in and hold your breath! Just stand normally. Measure three times and take
You’re at increased risk for diabetes and heart disease if you are:
While the WC has contributed more precision to the risk assessment than BMI
alone, we know that heart disease and diabetes occur in people who have
smaller waists than those cited above. This is especially true for people
with a BMI less than 30 (normal weight or overweight, but not obese).
There’s the possibility that increased fat around the waist, even though it
did not reach the WC threshold, would still put those people at additional
risk for heart disease.
- A woman with a waist circumference over 35 inches.
- A man with a waist circumference over 40 inches.
As a result, researchers recently decided to address that problem (2). They
combined anthropometric data from the NHANES III and the Canadian Heart
Health Study. Their goal was to increase the sensitivity and specificity of
the WC over all ranges of BMIs. Just like the WC threshold for men and
women, they wanted to determine if there are more specific WC thresholds for
people who were normal weight and less overweight. They used the Framingham
coronary heart disease risk index as the criteria for heart disease risk.
They found that indeed, there are varying WC measures that put people at
higher risk for heart disease even though they may not be overweight; the
table they developed is replicated below. It increases the specificity of
the BMI, especially for those whose BMI is in the Normal Weight and
Overweight categories. If your waist exceeds the threshold within a given
category, you are at a greater risk for heart disease, regardless of your
||Obese II and III
||18.5 to 24.9
||25 to 29.9
||30 to 34.9
If you find that your WC at your BMI category is more than it should be,
make an appointment with your physician and develop a plan for addressing
the issue. Remember--these simple measurements are an initial step. Your
physician can do additional testing of blood pressure and serum lipids to
make a more precise analysis of your health risk.
Your health is in your hands--don’t drop the ball! Better Life is here to
help you with the 30 Day Plan and the Walking book to get
your risk under control once again.
- Wilson, P and Grundy, S. The Metabolic Syndrome Practical Guide to
Origins and Treatment: Part I. Circulation. 2003;108:1422-1425.
- Ardern, Chris I., Ian Janssen, Robert Ross, and Peter T. Katzmarzyk.
Development of health-related waist circumference thresholds within BMI
categories. Obes Res. 2004;12:1094 –1103.