The human body can be divided into several constituent components. There are several levels that underlie the division of body composition, including division based on atoms, molecules, cells, and tissues.
- According to the atomic level, the composition of the human body is composed of oxygen, carbon, hydrogen, nitrogen, calcium, and other atoms.
- According to the molecular level, the composition of the human body is composed of fat and non-fat.
- Based on a cellular level, human body composition is composed of intracellular and extracellular.
- While based on tissue levels, the human body is composed of several tissues such as muscle tissue, fat, and bone.
According to J Brochek, body composition: 62.4% Water, 16.4% Protein, 5.9% Minerals, 15.3% Fat, 84.7% Free Fat Mass (FFM).
Body composition definition
Body composition is a body weight percentage consisting of non-fatty tissue and fat tissue. Assessing body composition is an important step in evaluating a person’s health status.
Body composition is defined as a relative proportion of fat tissue and fat-free tissue in the body. Body composition consists of four main components, namely total body fat, fat-free mass, bone mineral, and body water. The two most common components of body composition measured are total body fat tissue and fat-free tissue.
The human body consists of liquids and solids. Solids make up 40% of the human body, such as proteins, fats, minerals, carbohydrates, organic and non-organic materials, the remaining 60% are liquids. The division of 60% of the liquid composition, 20% is extracellular fluid and 40% is intracellular fluid.
According to Gilbert B Forber body composition is the total amount of body parts. Parts of the body consist of adipose and fat-free tissue mass.
While according to WHO, the human body is divided into 4 kinds of complex compositions consisting of:
- Atomic composition. Body weight is a lifelong accumulation of 6 main elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Less than 2 % of body weight consists of sulfur, potassium, sodium, chloride, magnesium and 40 other elements that are normally contained in amounts less than 10 grams.
- The composition of molecular. Elements are divided into molecular components grouped into 5 large categories, namely: fats, proteins, glycogen, water, and minerals. This molecular level is practically often divided over: fat and fat-free mass. This composition builds the basis for functional cells.
- Cellular composition. This composition consists of 3 components: cells, extracellular fluid and extracellular solid parts. Cell mass is further divided over the fat (molecular component) and the metabolically active part that is the body’s cell mass. So that it will eventually consist of body cell mass, extracellular fluid and extracellular solids.
- Composition of tissues and organs. Cells will form tissues and organs of the body, such as adipose tissue, skeletal muscles, bones, skin, heart, and other visceral organs. Tissues and organs of the body will form a human body that is a combination of 5 body components, namely atomic, molecular, cellular, tissues and organs as well as the body as a whole.
Body Composition Analysis Methods
There are many ways to determine your body composition. Some are quick and easy, but only provide basic information. Some are long-time and expensive, and need the help of trained technicians to conduct tests.
Here are some methods used to determine body composition:
One of the anthropometric methods used to measure body fat is the skin fold test. This is also known as a pinch test. As the name suggests, this method involves clamping the subcutaneous fat layer with the finger and measuring the thickness using a caliper.
Calipers are easy to carry around, and measurements are simple and inexpensive. However, this method involves estimating total Body Fat Percent (PBF) based on subcutaneous fat.
Although most body fat is subcutaneous fat, its measurements may not be accurate for people whose body fat distribution varies. Also, measurements are difficult if the thickness of the subcutaneous fat layer is 5 cm or more and the reproducibility of the result varies greatly depending on the measuring skill.
Underwater weighing calculates total body fat based on body density. It is based on the principle of Archimedes: when an object sinks in water, the difference between the mass of an object in the air and the mass in the water is the volume of that object.
Body density = Air mass / (Air mass – Water mass)
Underwater weighing is considered the gold standard for body composition measurement because it is the only body composition technology that has been directly compared to cadaver analysis.
Air Displacement Plethysmography
This method measures the volume of the human body by measuring the volume of air according to the change in pressure in a space.
First, people’s weight and volume are used to calculate body density and then body fat percent and fat-free ratios.
Density = Mass / Volume
Percent Body Fat = (495 / Density) – 450
Fat-free ratio = 100 – BF%
The time required for relatively short measurements is 3-5 minutes and test takers can continue breathing indoors as opposed to underwater weighing. This method is known as the gold standard because it enables analysis of body composition and produces accurate measurements using volumes such as underwater weighing.
Dual Energy X-Ray Absorptiometry (DEXA)
DEXA is an imaging method that measures weight in terms of bone mineral content, muscle mass, and fat with x-rays. With the patient lying down, photon x-rays of varying energy levels scan the patient. It takes about 5 to 30 minutes.
As the standard method for body composition analysis, DEXA has high accuracy along with hydrodensitometry. The advantage is that it can measure the composition of bone density, body fat and muscle mass for different parts. Technological advances give DEXA the ability to differentiate muscle and fat.
To perform a DEXA scan, you usually need to create a schedule with a hospital or clinic that has a DEXA device. And not all hospitals and clinics will have DEXA devices.
MRI (Magnetic Resonance Imaging)
An MRI is a form of imaging technique in which bodily fluids can be mapped (but not calculated in number). The body is scanned in segmental scans (slices) used to predict the value of the entire body. MRI is considered the most accurate tool for quantification of body composition in vivo. It is an ideal evaluation tool for measuring skeletal muscle mass and fat (and can divide fat into visceral and subcutaneous).
MRI uses high strength magnets, so all metals must be removed. A person with a metal chip, surgical clip, artificial joint/ prosthetic, pacemaker, metal implant, artificial heart valve, metal cochlear implant, bullet fragment, or insulin pump should not use an MRI.
Full-body scans are approximately 25-30 minutes for scanning and 3 hours for analysis through computer software.
Bioelectric Impedance Analysis (BIA)
Bioelectrical Impedance Analysis (BIA) is a method of measuring impedance by applying alternating electric current to the user to measure the volume of body fluids through impedance values.
This non-invasive method involves the placement of electrodes on the feet, hands, or both. A low-level electric current is sent through the body, and the current is affected by the amount of fluid in the body. BIA devices measure how these signals are inhibited through different types of tissues (muscles have high conductivity but fat slows down the electric current).
When the BIA determines resistance to current flow as it passes through the body, it provides an estimate of the bodily fluids from which body fat is calculated using the selected equations.