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Once you have your result, compare it to this chart to determine whether your amount of body fat falls into a healthy range.

BMI

CLASSIFICATION

< 18.5

= Underweight

18.5–24.9 25.0–29.9

= Normal

= Overweight

30.0 and above

= Obese

(Source: U.S. Centers for Disease Control and Prevention [CDC])

Here is a sample formula for a person who is five feet, three inches tall (63 inches) and weighs 120 pounds (notice we are using the U.S. rather than the metric formula):

[120 ÷ (63 x 63)] x 704.5 = BMI [120 ÷ (3969)] x 704.5 = BMI [.03] x 704.5 = 21.14

The person in our example has a BMI of 21 and thus falls within the normal range. Keep in mind that BMI ranges are simply practical guides for defining overweight and obesity. They are not rigid cutoff points. In fact, overweight and obesity classifications have proven difficult to pin down. The World Health Organization (WHO) describes obesity as “abnormal or excessive fat accumulation that may impair health,” but the exact point at which such impairment occurs is not precise and differs from person to person. The CDC states: “Simple, health-oriented definitions of overweight and obesity should be based on the amount of excess body fat at which health risks to individuals begin to increase. No such definitions currently exist.” Because precise definitions for overweight and obesity are elusive and

Weighing In: Defining the Problem / 17