Ask the doctor
Q. How can I measure my percentage of body fat? Is this good information to know?
A. Body fat percentage does provide information about your overall risk for diseases like heart disease and diabetes. Nutritional experts suggest a range of 10% to 25% body fat as healthy values for men.
Two methods are often used to determine body fat percentage. One is a skin fold measurement, in which a clinician measures certain areas of your body with calipers and uses the numbers to calculate a body fat percentage. However, this method is highly dependent on the accuracy of the measurements and can vary greatly. The second method is bioelectrical impedance analysis (BIA), in which a small electric current is sent through your body. Since water and fat conduct electricity differently, body fat can be calculated from this method. Still, BIA is less accurate when men have more abdominal fat and can be affected by how well hydrated you are.
There are easier ways to gauge your body fat. One is to compute your body mass index (BMI). BMI is calculated by dividing your weight in pounds by your height in inches squared and then multiplying by 703. (A BMI calculator can be found at www.health.harvard.edu/diet-and-weight-loss/bmi-calculator) For example, a six-foot, 160-pound man would have a BMI of 21.7. A BMI of 18.5 to 25 is considered healthy and is correlated with overall body fat. However, a BMI does not directly calculate fat percentage, and it can be misleading in extremely muscular individuals, as well as in older men, who may have low muscle mass.
Another measure of importance is waist circumference, since abdominal obesity is an important predictor of heart disease in men. You have a higher risk if your waist size exceeds 40 inches. Do you need to know your exact body fat percentage? Probably not. Body fat percentage remains more of interest in research studies and high-level athletics. Your BMI and waist circumference give you most of the information you need.
—William Kormos, M.D.
Editor in Chief, Harvard Men’s Health Watch