Health practitioners universally agree that too much body fat is a serious health risk. Problems such as hypertension, elevated blood lipids (fats and cholesterol), diabetes mellitus, cardiovascular disease, respiratory dysfunction, gall bladder disease, and some joint diseases are all related to obesity. Also, some research suggests that excessive accumulation of fat at specific body sites may be an important health risk factor (Wilmore, Buskirk, DiGirolamo, & Lohman, 1986). For instance, it appears that extra fat around the abdomen and waist is associated with higher risk of diabetes, heart disease, and hyperlipidemia. Individuals who accumulate a lot of fat around the waist (apple-shaped) are worse off than those who tend to accumulate fat in the thighs and buttocks (pear-shaped). The apple-shaped pattern of fat deposition is more commonly seen in men; whereas women tend to be pear-shaped.
Now, more than ever before, people are preoccupied with how much they weigh. New clients walk into our classes on a daily basis hoping that exercise will be the panacea. In an effort to lose weight and excess fat, Americans spent in 1989 an excess of 30 billion dollars for 54 million diet books and for services and products at 1500 weight control clinics (McArdle, Katch, & Katch, 1991). Yet, efforts such as these to achieve thinness are often based on popular misconceptions about body weight and body composition. Being thin does not necessarily reduce one’s health risk. In fact, obsession with becoming thin often leads to serious eating disorders such as anorexia and bulimia. Thinness simply refers to weighing less than the recommended values in age-height-weight tables. Leanness, on the other hand, refers to the muscle, bone, and fat composition of your body weight. Although some lean individuals may actually weigh more than their “tabled” ideal body weight, low body fat lessens the risk of health problems.
Understanding and being able to explain the difference between healthy leanness and undesirable thinness is one important concept the fitness instructor, personal trainer, and exercise leader must share with clients. In addition, there are some other reasons to become more informed about body composition:
Body Mass Fats Ratio :
- To develop complete physical fitness profiles for clients.
- To monitor body fat loss and muscle growth resulting from exercise.
- To provide baseline data for nutritional counseling and treatment of obesity.
- To describe changes due to growth, development, maturation, and aging.
- To maximize the performance of athletes.
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.
Standards of Body Fatnessary
Our bodies require essential fat because it serves as an important metabolic fuel for energy production and other normal bodily functions. Referring to Table 1, you can see that the essential fat requirements are < 5% for men and < 8% for women. Normal body functions may be disrupted if body fat falls below the minimum level recommended for men (5%) and women (15%). The body fat ranges for optimal health (18%-30% for women and 10%-25% for men) are based on several epidemiological studies of the general population. Body fat percentages for optimal fitness and for athletes tend to be lower than optimal health values because excess fat may hinder physical performance and activity.
When prescribing ideal body fat for a client, you should use a range of values rather than a single value to account for individual differences. After age 20, you should expect at least 1-3% fat gain per decade up to the age of 60; thereafter fatness declines gradually. In addition, there is approximately a 2% loss of bone mass per decade in older populations. As a result of these changes, men and women who weigh the same at age 60 as they did at age 20 may actually have double the amount of body fat unless they have been physically active throughout their life (Wilmore et al., 1986).
Table 1. Standards of Fatness for Women and Men in Percent Body Fata
Essential fat < 8 < 5
Minimal fat weight 15 5
Most athletes 12-22 5-13
Optimal health 18-30 10-25
Optimal fitness 16-25 12-18
Obesity > 30 > 25
a (Wilmore, J. H., Buskirk, E. R., DiGirolamo, M., & Lohman, T. G. (1986). Body Composition:
A round table. The Physician and Sportsmedicine, 14(3), 144-162.
Assessing Body Composition
The search for valid methods of measuring body composition that are practical and inexpensive is an ongoing process for exercise scientists and nutritionists. Standard age-height-weight tables derived from life insurance data often incorrectly indicate individuals to be overweight. Some practical methods of measuring body composition include skinfolds, circumference (girth) measures, hydrostatic weighing, bioelectrical impedance, and near-infrared interactance. Other advanced methods discussed in research journals include isotope dilution, neutron activation analysis, magnetic resonance imaging, and dual-energy x-ray absorptiometry. Most practical methods have a 3% to 4% error factor in their prediction of body fat (Brodie, 1988). That is, if you were measured at 20% body fat you could be as low as 17% or as high as 23%. This error factor may be increased dramatically due to the skill (or lack of it) of the technician taking the measurements.
Bioelectrical Impedance Analysis
Magnetic Resonance Imaging (MRI),
Computed Tomography (CT),
Dual Energy X-ray Absorptiometry (DEXA)