What is body composition, and why is it important?
Your body is made up of water, fat, protein, carbohydrate and various vitamins and minerals. If you have too much fat — especially if a lot of it is at your waist — you're at higher risk for such health problems
as high blood pressure, high blood cholesterol and diabetes (di"ah-BE'teez or di"ah-BE'tis). That increases your risk for heart disease and stroke.
Obesity is now recognized as a major, independent risk factor for heart disease. If you're overweight or obese, you can reduce your risk for heart disease by successfully losing weight and keeping it off.
Waist circumference and body mass index (BMI) are indirect ways to assess your body composition. Waist-to-hip ratio (WHR) is another index of body fat distribution. However, WHR is less accurate than BMI or waist circumference and is no longer recommended.
What is the waist circumference?
Waist circumference is the distance around your natural waist (just above the navel). If your BMI is greater than or equal to 25 kg/m2, your goal for waist circumference is less than 40 inches if you're a man and less than 35 inches if you're
What is the body mass index (BMI)?
Body mass index assesses your body weight relative to height. It's a useful, indirect measure of body composition because it correlates highly with body fat in most people. Weight in kilograms is divided by height in meters squared (kg/m2). 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. A BMI of about 25 kg/m2 corresponds to about 10 percent over ideal body weight. People with BMIs in this range have an increased risk of heart and blood vessel disease.
Obesity is defined as a BMI of 30.0 or greater (based on NIH guidelines) — about 30 pounds or more overweight. People with BMIs of 30 or more are at higher risk of cardiovascular disease.
Extreme obesity is defined as a BMI of 40 or greater.
Some well-trained people with dense muscle mass may have a high BMI score but very little body fat. For them, the waist circumference, the skinfold thickness or more direct methods of measuring body fat may be more useful measures.
How do you find your BMI risk level?
Use a weight scale on a hard, flat, uncarpeted surface. Wear very little clothing and no shoes.
Weigh yourself to the nearest pound.
With your eyes facing forward and your heels together, stand very straight against a wall. Your buttocks, shoulders and the back of your head should be touching the wall.
Mark your height at the highest point of your head. Then measure your height in feet and inches to the nearest 1/4 inch. Also figure your height in inches only.
Find your height in feet and inches in the first column of the Body Mass Index Risk Levels table. The ranges of weight that correspond to minimal risk, moderate risk (overweight) and high risk (obese) are shown in the three columns for each height.
(BMI under 25)
(BMI 30 and above)
118 lbs. or less
143 lbs. or more
123 or less
148 or more
127 or less
153 or more
131 or less
158 or more
135 or less
164 or more
140 or less
169 or more
144 or less
174 or more
149 or less
180 or more
154 or less
186 or more
158 or less
191 or more
163 or less
197 or more
168 or less
203 or more
173 or less
209 or more
178 or less
215 or more
183 or less
221 or more
188 or less
227 or more
193 or less
233 or more
199 or less
240 or more
204 or less
246 or more
To calculate your exact BMI value, multiply your weight in pounds by 703, divide by your height in inches, then divide again by your height in inches. (Adapted from Obesity Education Initiative: Clinical Guidelines on the Identification,
Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, Obesity Research 1998, 6 Suppl 2:51S-209S)