Body composition

Body composition describes parameters such as weight, height, shape, sex and body perimeters, among many others. These indices allow us to determine the percentages of fat, muscle, bone and water contained in human bodies.

The purpose of the study of body composition is to obtain an objective assessment of the nutritional status, which allows us to quantify the body reserves of the organism, to detect and correct nutritional problems such as the following:

• Existence of excess fats that indicate different degrees of obesity.

• Very low levels of muscle mass and fat mass, typical of organisms with nutritional deficiencies.

• Sports performance disorders in athletes due to loss of muscle mass.

• Follow-up of diets, in order to modify an inadequate body composition.

• It is essential to evaluate the nutritional status of vulnerable groups such as the elderly, children and pregnant or breastfeeding women.

Body compartments

Apart from water which constitutes more than half of the body weight and for the most part, is found in metabolically active tissues, the other two fundamental components of our body are:

• Lean tissue or fat-free mass.

• Adipose tissue or storage fat.

Lean tissue includes bones, muscles, extracellular water, nervous tissue and all other cells that are not fat cells. Muscle mass is the most important component and reflects the nutritional status of the protein.

Variations in lean tissue content:

• Lean tissue is greatest in males and increases progressively with age until the age of 20, decreasing thereafter in the adult.

• Lean tissue levels increase with physical activity.

Adipose tissue: fat plays an important role in hormonal metabolism and in the body's reserve and protection. It is differentiated by its location into subcutaneous fat, where the largest stores are located, and internal or visceral fat.

Variations in fat tissue content:

• Fat content, increases with age and is higher in women than in men.

• In men, fat tends to be deposited in the abdomen and upper body, while in women, it is deposited mainly in the thighs and hips. Fat deposited in the abdomen may represent a higher risk for developing some chronic degenerative diseases.

Techniques to assess body composition

Anthropometric techniques: this is one of the most widely used techniques to assess body composition. It is based on the use of very simple measurements such as weight, height, length of the extremities, and body perimeters, among others. These parameters allow the calculation of different indexes to estimate fat-free mass and body fat:

• Among the anthropometric techniques, the following stand out.

• Body mass index (BMI).

• Evaluation of body perimeters.

Body mass index (BMI): is a very useful parameter for assessing body composition. The body mass index allows the classification of people into underweight, normal weight, overweight and obese, based exclusively on height and weight. It does not take into account age, sex, body fat percentages or muscle mass. The (BMI) is calculated as follows:

• BMI is equal to body weight expressed in kilograms (kg), divided by the square of height expressed in meters (m).

• BMI = body weight (kg)/(height (m))².

For example: to calculate the body mass index of a man weighing 120 kg, who is 1.92 m tall, proceed as follows:

• Imc=120 kg / 1.92 m x 1.92 m

• Imc=120 kg / 3.68 m²

• Imc=32.6 kg/m²

Classification of persons according to body mass index, according to the World Health Organization.

In some cases these indexes do not directly reflect body composition. Examples:

• Athletes with well-developed muscles could have overweight indexes, however they have little fat.

• A marathon runner may be included in the underweight range, even if he or she is completely healthy.