The body fat percentage is a measure of fitness level, since it is the only body measurement which directly calculates a person’s relative body composition without regard to height or weight. Epidemiologically, the percentage of body ultrasound abdomen child training in an individual varies according to sex and age.
Various theoretical approaches exist on the relationships between body fat percentage, health, athletic capacity, etc. Different authorities have consequently developed different recommendations for ideal body fat percentages. In males, mean percentage body fat ranged from 22. In females, mean percentage body fat ranged from 32. Essential fat is the level at which physical and physiological health would be negatively affected, and below which death is certain.
Irrespective of the location from which they are obtained, the fat cells in humans are composed almost entirely of pure triglycerides with an average density of about 0. Most modern body composition laboratories today use the value of 1. With a well engineered weighing system, body density can be determined with great accuracy by completely submerging a person in water and calculating the volume of the displaced water from the weight of the displaced water. A correction is made for the buoyancy of air in the lungs and other gases in the body spaces. ADP uses the same principles as the gold-standard method of underwater weighing, but representing a densitometric method that is based on air displacement rather than on water immersion. A beam of infra-red light is transmitted into a biceps.
The light is reflected from the underlying muscle and absorbed by the fatileur . The method is safe, noninvasive, rapid and easy to use. X-rays of two different energies are used to scan the body, one of which is absorbed more strongly by fat than the other. A computer can subtract one image from the other, and the difference indicates the amount of fat relative to other tissues at each point. A sum over the entire image enables calculation of the overall body composition. There are several more complicated procedures that more accurately determine body fat percentage. Since fat tissue has a lower density than muscles and bones, it is possible to estimate the fat content.
This estimate is distorted by the fact that muscles and bones have different densities: for a person with a more-than-average amount of bone mass, the estimate will be too low. This section does not cite any sources. The general principle behind BIA: two or more conductors are attached to a person’s body and a small electric current is sent through the body. For convenience, an instrument which must be stepped on will also measure weight. There is little scope for technician error as such, but factors such as eating, drinking and exercising must be controlled since hydration level is an important source of error in determining the flow of the electric current to estimate body fat.
The instructions for use of instruments typically recommended not making measurements soon after drinking or eating or exercising, or when dehydrated. Population-specific equations are available for some instruments, making them more reliable. There exist various anthropometric methods for estimating body fat. The term anthropometric refers to measurements made of various parameters of the human body, such as circumferences of various body parts or thicknesses of skinfolds. Most of these methods are based on a statistical model.
Some measurements are selected, and are applied to a population sample. Because most anthropometric formulas such as the Durnin-Womersley skinfold method, the Jackson-Pollock skinfold method, and the US Navy circumference method, actually estimate body density, not body fat percentage, the body fat percentage is obtained by applying a second formula, such as the Siri or Brozek described in the above section on density. These methods are therefore inferior to a direct measurement of body density and the application of just one formula to estimate body fat percentage. One way to regard these methods is that they trade accuracy for convenience, since it is much more convenient to take a few body measurements than to submerge individuals in water.