How to calculate body fat percentage?

Body fat percentage

Body fat percentage is the weight of a person's fat divided by their total weight.
Total body fat includes essential and storage fat.

Essential fat: A person needs essential fat to survive. It plays a role in a wide range of bodily functions. For men, it is healthy to have 2 to 4 percent of their body composition as essential fat. For women, the figure is 10 to 13 percent, according to the Council on Exercise (ACE).

Storage fat: Fatty tissue protects the internal organs in the chest and abdomen, and the body can use it if necessary for energy.

Apart from the approximate guidelines for men and women, the ideal total fat percentage can depend on a person's body type or activity level.

ACE recommend the following percentages:

Activity level	Male body type	Female body type
Athletes	6–13%	14–20%
Fit non-athletes	14–17%	21–24%
Acceptable	18–25%	25–31%
Overweight	26–37%	32–41%
Obesity	38% or more	42% or more

A high proportion of body fat can indicate a greater risk of:

• Diabetes
• Heart disease
• High blood pressure
• Stroke

Calculating body fat percentage may be a good way to measure a person's fitness level because it reflects the person's body composition. BMI, in contrast, does not distinguish between fat and muscle mass.

 How to measure body fat

Calipers

Calipers measure body fat. The result can give an indication of whether a person is likely to have certain health risks.

The most common ways of measuring body fat percentage is to use a skinfold measurement, which uses special calipers to pinch the skin.

The health professional will measure tissue on the thigh, abdomen, chest (for men) or upper arm (for women). The techniques provide an accurate reading within around 3.5 percent, according to ACE.

Other techniques include

Underwater weighing

Underwater weighing also called Hydrostatic weighing and is based on principle of Archimede which tells us that a buoyant force acts on a body immersed in a liquid equal to the weight of the volume of liquid displaced by the part of the body immersed in this liquid. Using this principle allow you to measure body fat percentage, because the density of fat mass is around 0.9 kilograms per litre, when the fat free mass density such as muscle and bone is 1.1 kilograms per litre.

Air displacement plethysmography

Whole-body air displacement plethysmography or ADP. In this case, used a special device called Bod Pod. The principle of operation of this device is somehow similar to underwater weighing, only in this case air is used instead of water. This device measures the volume of the body based on the physical relationship between pressure and volume.

Bioelectrical impedance analysis

The essence of this method is that two electrodes are placed on the human body, usually on the person’s hand and foot. Then a very weak electric current is passed through the body and the device specifically reads and analyzes the signal attenuation. The amount of resistance in this case helps to determine the percentage of fat in the body, since adipose, muscle and skeletal tissue have different levels of resistance to electricity. Muscles have good conductivity because they contain about 70% of water, while fat practically does not contain water, and therefore is a poor conductor.

Ultrasound

Ultrasound measurement of subcutaneous fat thickness is one of the most accurate and at the same time expensive methods. For measurements, special devices are used that are based on the use of tabular values of the speed of sound in body tissues and analysis of signals to determine the thickness of fat. By measuring the thickness of fat in various parts of the body, you can calculate the estimated percentage of fat in the body.