Body Mass Index (BMI - a measure of body fat) Guide

Calculating Body Mass Index (BMI)
The body mass index (BMI) is derived by multiplying a person's weight in pounds by 703 and then dividing by the height in inches, then dividing that number by the height in inches.

Multiply one's weight in pounds by 703.
Divide that answer by height in inches.
Divide that answer again by height in inches.

For example, a woman who weighs 150 pounds and is five feet eight inches (or 68 inches) tall has a BMI of 22.8. The result is graded on a scale to indicate levels of body fat. Federal guidelines define the following:

Being overweight is a BMI of 25 to 29.9, and
Obesity as a BMI of 30 or greater.

These guidelines are very important for people at risk for diabetes, heart disease, or certain cancers.

Waist Circumference and Waist-Hip Ratio. The extent of abdominal fat is also used in assessing risk of disease. Some studies suggest the following:

Women whose waistlines are over 31.5 inches and men whose waists measure over 37 inches should watch their weight.
A circumference of greater than 35 inches in women and 40 inches in men has been associated with an increased risk for heart disease, diabetes, and impaired functioning. (In one 2000 study, a high triglyceride level along with a waist measurement of over 36 inches was a particularly strong predictor of heart problems in men.)

Evidence strongly suggests that an unequal distribution of body fat around the abdomen and compared to the hips (the apple-shape) is a more consistent predictor of health risks than BMI or waist circumference alone.

The distribution of fat can be evaluated by dividing waist size by hip size. For example, a woman with a 30-inch waist and 40-inch hip circumference would have a ratio of .75; one with a 41-inch waist and 39-inch hips would have a ratio of 1.05. The lower the ratio the better. The risk of heart disease rises sharply for women with ratios above 0.8 and for men with ratios above 1.0.

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