Whats Your Body Fat Percentage - Are You Overweight: Obesity

Content provided by the Faculty of the Harvard Medical School

What's your body fat percentage?

You can estimate your body fat percentage by several different methods, but be aware that these tools aren't always accurate and doctors don't consider them useful to guide treatment. In general, these methods tend to be less accurate in people with obesity than in people who are slightly overweight or at a normal weight. But some athletes and people who are trying to tone their bodies while losing weight may find it motivates them to keep tabs on their body fat percentage. Healthy adult men have body fat percentages between 10% and 25%, whereas the range for women is between 18% and 32%. Higher percentages are considered abnormal and consistent with obesity. In children, body fat percentages above 25% in boys and 30% in girls are associated with being overweight.

Skin-fold thickness. A technician or health professional uses calipers, a measuring instrument, to gauge the thickness of a fold of skin on the body at several different sites, such as the upper arms, waist, and thighs. The measurements are entered into a formula to produce an estimate of body fat percentage. This method gives a reasonable estimate, but results often vary when different people take the measurements, making this test not very reliable.

Bioelectric impedance. This test uses a small, harmless electrical current to measure the electrical resistance of the body, based on the principle that lean body mass conducts electricity faster than fat body mass. Special "body fat" scales that use this principle in combination with your height and weight can calculate your body fat percentage. Results can vary with the amount of water in your body and are considered unreliable in people with obesity.

Underwater weighing. This test, based on the principle that fat tissue is less dense than muscle and bone, uses a special bathtub-sized tank to weigh a person underwater. That weight is then compared to the person's weight on land; a formula identifies the percentage of body fat that would account for the difference. Underwater weighing is considered the most accurate method, but it is generally available only at universities and research facilities.

Last updated:	June 20, 2007