Body composition is the aggregate of the composite parts of the human structure. The body is made of water (as contained in both intracellular and extracellular formats, the latter being primarily blood plasma), fats, proteins, stored carbohydrates, vitamins, and minerals. The chief divisions of body composition are lean body mass and body fat, often expressed as the percentage of body fat.
Lean body mass is the total of the internal organs, skin, bones, connective tissues, and muscle. Each of these structures is formed from one or more of the body's essential ingredients. Lean body mass components are each active organisms, all of which consume energy at all times, either through function, as in the case of an internal organ or system; or through fueling and sustenance, as required by muscles, connective tissues, and bones.
Body fat is an expression that has developed a negative connotation in recent years, as elements of Western society become more conscious of factors that tend to impair general health; excess body fat is a contributor to many types of human illness and disease. Body fat is a natural part of healthy human function, essential to good health when in the correct proportion to lean body mass.
The determination of the ideal proportion of lean body mass to body fat is not possible to a mathematical certainty. As a general proposition, body fat is defined as the dietary fats stored in the specialty cells of the body known as adipose tissues. Adipose tissues are predominant on females in the abdomen, hips, thighs, and breasts, while males have a greater proportion on the lower abdomen, chest, and buttocks. Body fat is also stored in both sexes near a number of internal organs; the amount of body fat stored in this fashion increases after age 35. The human body is constructed in such a fashion that this additional body fat serves to protect and insulate the body; it is excess amounts of body fat that pose significant health concerns.
Body composition is also influenced by genetic factors. Body types can be classified as three general types: mesomorphic, a tall, muscular build; ectomorphic, a taller, thin, lightly boned build; and endomorphic, a shorter, stockier, rounder build.
The correct proportion of body fat for an individual must be assessed considering a person's overall general health, age, gender, and level of physical activity. The so-called ideal weight is therefore variable, even between persons with similar builds. By way of very general boundaries, a healthy athletic male will expect to have a body fat percentage of 10% or less; a similar female, due to the genetic differences between male and female body composition, might possess body fat in the range of 14% to 18%. At the opposite end of the health spectrum, the obese male and female will exceed 30% body fat.
There are a multitude of diets advertised as assisting in the reduction of body fat, and consequently, overall weight loss. In considering the benefits of such diets, it is important to consider how the body naturally uses foods. A governing rule of all bodily functions is the principle of seeking balance, a concept known as homeostasis. With weight control, where the amount of physical activity requires energy equal to that available from the amount of food consumed, the body will remain at a constant weight. When the amount of food consumed exceeds the body's energy requirements, the body will gain weight, and the excess energy supply will be stored as body fat. When the energy requirements of exercise exceed the energy available through the food consumed, the body will, over time, use its stored body fat energy supply. This relationship is unalterable.
The methods by which an individual can measure present body fat composition are varied, from the low technology and highly inaccurate body mass index (BMI) to hydrostatic weighing. The BMI is a calculation of the person's total body mass divided by the product of height and weight. The BMI calculation is then assessed in relation to a scale. The BMI cannot provide a concrete body fat figure for an individual because the index does not involve any direct measurement.
Skin fold measurement is conducted using skin calipers to measure the thickness of the skin fold in the upper arm/triceps, chest, abdomen, hips, and buttocks, each of which are areas where body fat naturally is stored in adipose tissue. Hydrostatic weighing applies the Archimedes principle, where the amount of water displaced by immersion of the individual represents the fat present. Hydrostatic weighing is accurate to within approximately 3%.
Once the individual's body fat percentage has been accurately determined, the individual can make intelligent decisions regarding the elimination of excessive body fat. For an athlete, the decision must be one of function, both present and future, as opposed to form.