Most Common Tests To Monitor Fat

Human body consists of two types of fat, the essential fat and the body (storage) fat. Essential fat is responsible for metabolism and consist of fats stored in the lungs, heart, kidneys, liver, spleen, intestines, bone marrow, muscles, and in parts of the central nervous system.

Body fat is loose connective tissue (adipose tissue), which store energy in the form of fat. In fact, storage fat play an important role in protecting the internal organs of the body and in supplying energy at times of need. However, too much accumulation of body fat leads to a condition called obesity.

A person's body weight is defined as a measure of the total lean body mass (mass of organ, bone, muscle, and water) and fat mass. The recommended body weight for a person depends upon his/her height. The general tool used for analyzing a person's healthy body weight based on his/her height is known as body mass index (BMI).

A person having a BMI of 25 kg/m² or more is considered to be overweight. Similarly, a person is called obese if his/her BMI is 30 kg/m² or higher.

Considering the overall fitness and well-being of a person, the body fat percentage is more important than the overall weight. Monitoring body fat is an important way to determine the percentage body fat. Certain techniques are used to estimate the percentage of body fat, and some of them include:

BIA is a commonly used technique to calculate the percentage of body fat by analyzing the electrical resistance generated due to fat of the body. These monitors are easy to operate and are also available for home use. It is a fact that the conductivity or impedance of various tissues of the body varies and this forms the principle for this technique.

A very low voltage electric signal is passed to the body and impedance of the lean tissues and fat tissues are measured. Since lean tissues have a higher water content, the conductivity is more as compared to fat tissues which have less water content. BIA devices use the data and find the body fat percentage. The inaccuracy percentage of BIA is found to be +/-3%.

NIR is a method of analyzing body fat based on the principle of light absorption and infrared spectroscopy (practice of measuring the emission and absorption of different wavelengths of infrared light). It uses colors for different body surfaces, such as biceps and hips along with a computerized spectrophotometer that analyzes the emitted infrared light.

Values of reflected light for muscles and fat are different and are taken into consideration for the measurement of body fat. Although this method is safe, fast, and convenient, its use is limited because of the lack of accuracy.

DEXA is the most popularly used scanning tool for the determination of bone density. It can also be used for the assessment of the total body composition and fat distribution. The principle used is based on the fact that the density of a bone is directly proportional to the amount of photons absorbed by the particular bone.

These types of monitors use two radiations of different wavelengths at a set frequency to measure the bone density, lean body mass, and fat mass. DEXA is a quick, accurate, and reliable tool, however, the disadvantage is that DEXA machines are very costly.

Calipers are used for analyzing body fat by measuring the skinfold thickness. In this method, hand-held calipers are used for estimating the subcutaneous tissue. The sites for skin fold measurement vary for men and women. For example, chest, abdomen, and thigh are measured in case of men, whereas tricep, suprailiac, and thigh are measured for women.

Calipers are an easy and inexpensive way of estimating body fat. However, it is difficult to measure the skinfold of an obese person. The accuracy of this tool depends upon the quality of the calipers and the skill of the technician.

At present, body fat monitors are becoming more popular than the traditional weighing machines. Other monitors include hydrodensitometry weighing (underwater weighing to determine body density), magnetic resonance imaging (scanning procedure to analyze lean body mass, bone and body fat) and total body electrical conductivity (technique that determines lean body mass and fat based on their conductivity).