There are a variety of ways to measure the amount of body fat a person is carrying.
“The most accurate way is ‘underwater weighing,’ which weighs the person on land and then underwater,” says Mary M. Flynn, PhD, RD, chief research dietitian and assistant professor of medicine at the Miriam Hospital and Brown University in Providence, R.I. “But equipment for this is very expensive and not readily available.”
Another fairly accurate option is Bioelectric Impedance Analysis (BIA). BIA consists of electrodes being placed on a person’s hand and foot while a current (which is not felt) is passed through the body. Fat has less water and is more resistant to the current, whereas muscle, which contains more water, is less resistant. The resulting numbers are entered into an equation which figures the percentage of fat and lean tissue.
The easiest method is measuring waist circumference and determining the Body Mass Index (BMI). A waist circumference over 35 inches for women and 40 inches for men is cause for concern.
Figuring BMI involves a little more calculation. BMI is done by multiplying your weight in pounds by 703, then dividing that number by your height in inches two times. If the end result is less than 18.5, the individual is underweight;18.5 to 24.9 is normal; 25.0 to 29.9 is overweight; and over 30 is obese.
“However, you must be aware of this disclaimer. BMI alone is not an indication of body fat, especially in athletes and body builders. Growing children under 18 years old should also avoid using BMI,” says Elizabeth Downs, RD, clinical dietitian at the Montefiore Medical Centre at the University Hospital for the Albert Einstein College of Medicine in the Bronx, N.Y.
One final way of determining body fat is using skin callipers to measure fat at specific places in the body. However, not only is it easy to make errors, but this method also doesn't
measure any interior fat or fat contained in thighs and women’s breasts.
Ultimately the percentage of body fat is just another number in the health equation. And if you are not happy with the result, all it takes is adding exercise and cutting calories to get it moving in the right direction.