How to Measure Body Composition

Body composition assessment re­quires the separation and quantifica­tion of lean tissue from fat. Many indirect methods for measuring this component have been developed but we will focus on just one—skinfold measurements.

Lean tissue includes all tissue except fat: muscle, bones, organs, fluid, and the like. Fat includes both essential and storage fat. Essential fat, found in the bone marrow, organs, muscles, intestines, and central nervous system, is indispensable to normal physiological functioning.

The amount of essential fat in the male body is equal to approximately 3 percent to 5 percent of the total body weight. The amount of essential fat in the female body is equal to about 11 percent to 14 percent of the total body weight. The disparity in the amount of essential fat between the sexes is probably because of sex-specific essen­tial fat stored in a female’s breasts, pelvic area, and thighs. Essential fat constitutes a lower limit beyond which fat loss is undesirable and unhealthy because of the possibility of impaired normal physiological and biological functioning from such loss.

Storage fat is found in adipose (fat) tissue. For most people, this represents a substantial energy reserve. Adipose cells are found subcutaneously (under the skin) and around the organs, where they act as a buffer against physical trauma. Reducing excess storage fat is desir­able for health and aesthetic reasons. Reasonable goals for total body fat (essential plus storage fat) differ by sex. Excellent values for males and females are 12 percent and 20 percent, respectively. Males are overfat when 25 percent or more of their weight is in the form of fat. Females are overfat when 32 percent or more of their weight is in the form of fat.

Skinfold measurement became more common after several low-cost calipers made their way into the mar­ketplace. In skilled hands, some of them correlate quite well (.90) with the more expensive brands found in most exercise physiology labs. The rationale for the skinfold tech­nique is that approximately half of the body’s fat is located directly beneath the skin. Therefore, the skinfold— which consists of a double layer of skin and the underlying fat—can be measured using a caliper.