Endocrine Disorders

For a Body Fat Tip Off, Look to Your BMI...

Over half the American population is overweight, and nearly one quarter are obese. People don’t need studies or experts to know that a growing girth will take a toll on their health. But it may take more than a mirror or an arbitrary "goal weight" to get on a leaner road.

Experts have found that body mass index, or BMI may be a better indicator of health risk than absolute body weight. In addition, where you gain the weight may be equally important in determining your risk for certain diseases. Though it is only one of a number of considerations that health experts use to determine these risks, BMI is more highly correlated with body fat than any other measurement of height and weight. Below, Anne Wolf, obesity expert and instructor of research at the University of Virginia School of Medicine, offers simple instructions for determining body mass index, and talks about the usefulness of BMI in assessing health risk and as a goal for weight loss.

What is body mass index, or BMI, and what does it measure?
Body mass index uses a person's height and weight to assess that person's risk of health problems.

How is measuring BMI different from just asking someone to step on a scale?
Weight alone is not a very good measure of body fat. BMI is highly correlated with body fat, and, subsequently, health risk.

Is BMI a new way to assess a person's health risk?
Doctors used to assess a person's "ideal" weight using height measurements, but they then realized that it was sending a very bad message. It implied that each person has an ideal weight for their height, which is not true. In fact, there is a range and it is more useful to understand that by falling into certain categories your risk of diseases goes up. BMI is based on health risk, not on how you look.

How is BMI calculated?
The formula is a little complicated. The first step would be to multiply your weight in pounds by 703. Next, square your height in inches. So if you are 65 inches tall, you're going to multiply 65 by 65. The third and last step is to divide your weight by your height. That will give you your body mass index. For instance, if you are 124 pounds and 5 feet tall (60 inches), your BMI would be 24.2.

And what is considered a healthy and an unhealthy BMI?
A BMI of less than 18.5 would be underweight. A BMI between 18.5 and 24.9 would be considered a healthy body weight. Overweight is categorized as 25 to 29.9, and obesity is categorized as a BMI of 30 and above.

Does BMI account for body proportion?
No. And in fact, one of the other measurements that the National Heart, Lung and Blood Institute recommends using waist circumference with BMI to access your health risk. Experts know that a high waist circumference-or a high amount of abdominal body fat-is very dangerous, and independent of a high body mass index.

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