What is Body Fat Composition?
A person's body fat percentage is the total weight of the person's fat divided by the person's weight and consists of essential body fat and storage body fat. Essential body fat is necessary to maintain life and reproductive functions. The percentage for women is greater than that for men, due to the demands of childbearing and other hormonal functions.
The American Council on Exercise provides the following ranges for men and women with classifications based on varying levels of body fat:
- Essential fat is 2-5% in men, and 10–13% in women.
- Athlete: 6-13% men, 14-20% women
- Fitness: 14-17% men, 21-24% women.
- Average: 18-24% men, 25-31% women.
- Obese: 25% and above men, 32% and above women.
Source: American Council on Exercise (2003) ACE Personal Trainer Manual, 3rd Ed., Ch. 6, Pg. 188, Table 6.14, General Body Fat Percentage Categories
What is Body Composition?
Body Composition: The body is composed of water, protein, minerals, and fat. A two-component model of body composition divides the body into a fat component and fat-free component. Body fat is the most variable constituent of the body. The total amount of body fat consists of essential fat and storage fat. Fat in the marrow of bones, in the heart, lungs, liver, spleen, kidneys, intestines, muscles, and lipid-rich tissues throughout the central nervous system is called essential fat, whereas fat that accumulates in adipose tissue is called storage fat. Essential fat is necessary for normal bodily functioning.
The essential fat of women is higher than that of men because it includes sex-characteristic fat related to child-bearing. Storage fat is located around internal organs (internal storage fat) and directly beneath the skin (subcutaneous storage fat). It provides bodily protection and serves as an insulator to conserve body heat. The relationship between subcutaneous fat and internal fat may not be the same for all individuals and may fluctuate during the life cycle. Lean body mass represents the weight of your muscles, bones, ligaments, tendons, and internal organs.
Lean body mass differs from fat-free mass. Since there is some essential fat in the marrow of your bones and internal organs, the lean body mass includes a small percentage of essential fat. However, with the two-component model of body composition, these sources of essential fat are estimated and subtracted from total body weight to obtain the fat-free mass. Practical methods of assessing body composition such as skinfolds, bioelectrical impedance analysis (BIA), and hydrostatic weighing are based on the two-component (fat and fat-free mass) model of body composition.