Body fat percentage is a measurement obtained by dividing total body fat mass divided by total body mass. Total fat includes both essential body fat and storage body fat, and it applies not only to humans, but also to other living things. It is measured by various techniques such as electrical bioimpedance analysis or caliper measurements.
Essential body fat is the fat that the body needs for normal physiological functions, for example for reproductive function. Women tend to have a higher percentage of essential body fat, around 10-13% compared to 2-5% in men, as it is part of female tissues such as the mammary glands. Below these levels of body fat, health and some physiological processes can be adversely affected.
Storage body fat is fat that is deposited in white adipose tissue in different parts of the body, mainly under the skin and around organs and viscera, and whose function is to store energy and protect it. While this body fat is not essential, its function is important and therefore the recommended body fat percentage is strictly higher than the essential fat percentage.
Body fat percentage is a measure of relative body composition regardless of height or weight, so it is generally understood as a measure of fitness level and can also be related to health level, risk factors for some diseases, and physical ability at general.
Average body fat percentages
From an epidemiological point of view, average body fat varies mainly with three factors: sex, age and physical activity.
In women, the percentage of body fat usually increases from adolescence to adulthood with average values between 30 and 40%. In men, however, it usually decreases during puberty and youth to gradually increase in a less pronounced way until adulthood, with values between 20 and 30% on average.
There are many methods to measure body fat percentage, with anthropometric and electrical bioimpedance methods being some of the most used, mainly because of their low cost, although they are not the most accurate.
Anthropometric methods are estimates based on different measurements. One of the most used is the thickness of the fold between the muscle and the skin surface in certain areas of the body, such as the abdomen and forearm, which is converted into an estimated percentage of body fat through standardized formulas, usually already integrated into simple devices such as calipers or calipers.
Another widely used anthropometric method is the estimate from the Body Mass Index, height and circumference.
The bioelectrical impedance method consists of passing a small electric current through the body and measuring the conduction resistance offered by the body, with muscle being a good conductor of electricity and adipose tissue a poor conductor. the greater the resistance, the greater the percentage of fat.
Adipocytes, the fat cells of adipose tissue, are essentially composed of triglycerides with an average density of 0.9 kg/L. Based on this value, one of the most accurate methods for measuring body fat percentage is hydrostatic weight, which measures body weight and water displacement when completely submerging a person’s body in water. A system based on similar principles is body displacement air plethysmography. Another even more accurate method is X-ray Absorbimetry.