A two-component model of body composition divides the body into fat component and fat-free component. The total amount of body fat consists of essential fat (fat in the marrow of bones, in the heart, lungs, liver, spleen, kidneys, muscles and central nervous system) and storage fat (fat that accumulates in adipose tissue, located around internal organs and subcutaneous). 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 our muscles, bones, ligaments, tendons and internal organs. Lean body mass differs from fat-free mass. Lean body mass includes a small percentage of essential fat (essential fat in the marrow of bones and internal organs) (8).

Of this lean body mass, the component that can change the most is muscle tissue.

There are several approaches to body composition assessment. Underwater weighing and DEXA (dual energy X-ray absorptiometry) are the only body fat testing methods that have been scientifically validated and thus, are considered the “gold standard”, but they are expensive and impractical for most people (6).

In sports practice, assessment of body composition is based on skinfold test. The skinfold method of measuring body fat is practical, economical, accurate and non-invasive (2). Results come close to underwater weighing and DEXA, but the technique requires much practice to obtain accurate results. In this respect, INMS has an experience for more than 40 years and the method proved its validity. Measurements are taken with a caliper at several body sites. Results, expressed in mm, are put into a formula to calculate body fat and lean body mass percentage.

Body fat percent varies considerably with gender, age, athletes and non-athletes.A certain amount of body fat is necessary for health and body functioning. Essential fat is necessary for bodily functioning and the essential fat of woman is higher than that of man.

Optimal health body fat in adults’ non-athletes is 12-18% (10-25%) for men and 16-25% (18-30%) for women (9).

The body fat percent for elite athletes varies largely by sports: 6-13% (19% throwers and harder categories) for men and 12-19% for women.

Changes in athletes’ body weight and body composition are correlated to state of training, training level and caloric intake.

In most sports the athlete will try to keep his/ her levels of body fat to a minimum.

Being overweight (body-building, canoe) is not a problem if there is very good lean body mass and low fat tissue. The athletes who has a very good lean body mass is able to have a high level of subcutaneous fat (rugby, throwers in athletics), but this growth mustn’t associate with high level of blood lipids and cholesterol (4).

Swimmers, especially female swimmers, have % body fat higher than long distance runners or cyclists.

In sports as gymnastics, distance running, jumping, etc the athletes must be underweight with good lean body mass and few body fat.

The ideal body weight and body composition are essential in artistic gymnastics, because the exercises are made against gravitation.

Also the body composition and body fat is important for weight category sports (as judo, wrestling, boxing, weight lifting) in order to choose the realistic weight category. If an athlete already has low body fat, then significant weight loss could only be achieved by loss of lean body mass, which can compromise strength and endurance capacity (3).

Aesthetic sports such as gymnastics, diving, figure skating are in essence weight category sports, as a low body mass and an ideal body composition are requirements.

Assessment weight and body composition give us useful information for athletes’ training and nutrition.

Assessment of body composition is also useful in childhood and adolescence in order to appreciate nutritional status and monitor corrective treatment.

Usually, BMI is used to estimate one’s normal weight. But, body weight and BMI do not give information about body fat (7). Some well-trained people with muscle mass may have a high BMI score but very little body fat. There are people who are at the standard weight for age-sex-height (or under this weight), but they have too much fat. There are also people (especially women) who have very low body fat tissue that is harmful for women.

Research has shown that beginning about adulthood lean mass get down and fat tissue get up. Even people who maintain their standard weight lose muscle tissue and gain fat due to sedentary lifestyle of too little exercises and too much fat in the diet. Using proper exercises and diet program it is possible to build muscle tissue in adults and elderly.

The size of adipose tissue mass depends of the number and the size of lipid-filled cells. An increase in adipose tissue can occur by an increase in the number of adipocytes (hyperplastic growth) or by an increase in the size of adipocytes by lipid accumulation within the cell (hypertrophic growth). Hyperplastic growth occurs in childhood pre-adolescence and adolescence, and once new adipocytes are formed, they remain throughout life. This increased number of adipocytes has negative far-reaching consequences.

Obesity is a chronic disease more and more frequent in childhood and adolescence due to incorrect diet and insufficient physic activities, and the over-weight child is predisposed to obesity in adulthood. It is the quantity of adipose tissue and not just total body weight that defines obesity (1). Obesity is now recognized as a major, independent risk factor for heart disease and diabetes. That’s why is very important to keep a good weight and body composition during childhood.

Assessment of body composition is important to monitor the effect of diet and/or exercise on muscle tissue and fat. Persons who lose weight on a typical fad diet lose as much or more muscle than fat. Other times, even if someone starts on a good exercise program combined with a proper diet, their weight is not changing in first weeks-months, but they were replacing fat with muscle. The benefit of exercise during weight loss diet is that it results in preservation of fat-free mass and allows fat loss that is equivalent to or greater then weight loss(5).

The way to reduce properly is through exercise combined with a proper well-balanced diet (in any case by starvation) and by monitoring periodically body composition (body fat percentage).

References

1. Albright,A.L., Stern, J.S.(1998). Adipose tissue.Encyclopedia of Sports Medicine and Science.

2. Brodie, D. A. (1988). Techniques of measurement of body composition Part II. Sports Medicine, 5, 74-98.

3.  Burke, L., Deakin, V.(2002). Kinanthropometry: physique assessment of the athlete. Clinical Sports Nutrition (2 nd ed), 4,69-89.

4. Dragan, I. , et al. Evaluarea dezvoltarii fizice la sportivi. Medicina sportiva, 2002; 214-35.

5. Heyward, V. H. Advanced fitness assessment & exercise prescription. Champaign : Human Kinetics Publishers.(1991).

6. Lohman, T.G., et al. Assessing body composition and changes in body composition. Another look at dual-energy X-ray absorptiometry. Ann NY Acad Sci 2000; 904-45.

7. Maynard, L. M., et al. Childhood body composition in relation to body mass index. Pediatrics 2001; 107-344.

8. McArdle, W. D., Katch, F. I. & Katch, V. I.(2001). Body composition assessment. Exercise physiology: Energy, nutrition and human performance (5 rd ed). 752-93.