Waist circumference measurement and body mass index (BMI) are the recommended ways to estimate body fat. A high-risk waistline is more than 35 inches for women, more than 40 inches for men.
The body mass index formula assesses body weight relative to height. It's a useful, indirect measure of body composition, because in most people it correlates highly with body fat. BMI is calculated by dividing a person's body weight in kilograms by their height in meters squared (weight [kg] height [m]2) or by using the conversion with pounds (lbs) and inches (in) squared as shown below. In studies by the National Center for Health Statistics,
BMI values less than 18.5 are considered underweight.
BMI values from 18.5 to 24.9 are healthy.
Overweight is defined as a body mass index of 25.0 to less than 30.0 (consistent with U.S. Dietary Guidelines for Americans). A BMI of about 25 kg/m2 corresponds to about 10 percent over ideal body weight.
Obesity is defined as a BMI of 30.0 or greater (consistent with criteria of the World Health Organization), or about 30 pounds or more overweight. Extreme obesity is defined as a BMI of 40 or greater.
