By Elena Voropay

Body Composition is the technical term used to describe the different components that, when taken together, make up a person's body weight. It refers to the relative percentages of fat and nonfat tissues (or lean body mass). Now you must keep in mind that body composition and body weight are two entirely different concepts, and they are not interchangeable. To get a better understanding of the difference between the two, you need to understand a bit about anatomy and physiology.

You probably realize that the human body is composed of a variety of different tissue types. The so-called 'lean' tissues, such as muscle, bone, and organs are metabolically active, while adipose, or fat tissue, is not. Since scientists like to classify things, they have divided adipose tissue into three different categories:

1. Essential fat, which supports life, and is extremely important to normal bodily function. Infertility, depression, impaired temperature regulation, and even death are among teh outcomes of excessive fat loss.

2. Storage fat, that protects internal organs and supplies some energy requirements, helps temperature regulation, and cushioning the joints.

3. Non-essential fat, serves no real purpose, and may, in fact, be detrimental to health.

The difference in these tissues is not readily distinguishable by stepping on a scale. A scale simply takes the sum of everything (fat, muscle, water, hair, you name it), and gives an absolute weight measurement. Simple weight scales can't determine the lean-to-fat ratio of that weight. An individual can be "over-weight" and not "over-fat." A bodybuilder, for example, may be 8% body fat, yet at two hundred and fifty pounds may be considered "over-weight" by a typical height-weight chart. Therefore, these charts are not a good indication of a person's ideal body weight for optimal health, much less for athletic performance.

Body Composition Assessment

In order to identify these tissues, physiologists have developed several different methods of assessing the percent of fat vs. lean mass of an individual. These methods are referred to as Body Composition Analysis. There are many methods of assessment.

A relatively quick but expensive procedure developed for measuring the density of bones can now estimate body fat percentage. Dual-energy X-ray abosorptiomenty (DEXA) is considered to be the gold standard of estimating body composition, providing very accurate results for all gender, age, and race groups tested. The software determines the density of all parts of the body, including fat, bone mineral, and non-bone leat tissue, through a total-body X ray using extremely low dosage energy beams. Because of the compexity and cost of the procedure, DEXA equipment is housed in clinical settings only.

Hydrodensitometry (hydrostatic or underwater weighing) is based on the principle that bone mineral is more dense than muscle tissue, which is more dense than fat. This technique employs immersing a body in water and calculates body density by measuring underwater and out-of-water weight, corrected by density of water. Hydrostatic weighing is a time consuming, expensive, anxiety-provoking and complicated procedure, and requires special equipment.

Anthropometric assessment using measurements of height, weight, circumferences, and skinfolds is the most common approach. Methods include Body Mass Index, Waist-to-Hip Circumference, and Skinfold Measurements (7-Site or 3-Site formulas are most accurate). However, Bioelectrical Impedance Analysis (BIA) is growing in popularity being relatively inexpensive, rapid, and non-invasive method of assessment. In conventional BIA, before a person is weighed, his/her height, age and gender are entered in the system. The device provides electrodes that are attached to various parts of the body. A small electric current is discharged measuring the impedance or resistance to muscle and fat. The more muscle, the lower the value as the electricity passes easily through lean mass. A formula in the computer converts all of the data to indicate what percentage of the body is fat. Lean tissue is a good conductor of electrical current, whereas fat is not.

What should your body fat percent be?

Body fat percent varies considerably for men and women, for age and culture for those involved in different sports activities, and even for different geographic location. However, there are some recommendations based on different studies of body fat levels that may be associated with improved physical performance.The minimum percent bodyfat considered safe and acceptable for good health is 5% for active males and 12% for active females. The average adult bodyfat is closer to 15%-18% for men and 22%-25% for women. Some increase in percent fat with age is permitted as it reduces the risk for osteoporosis and bone fractures due to low bone mineral content found in middle-age women.

How Low Is Too Low?

It has long been known that thin people will die first during a siege or in a famine. Underweight increases the rist for any person fighting a wasting disease. In fact, people with cancer often die, not from the cancer itself, but from starvation. As previously mentioned, body fat is required to serve as an evergy reserve and as protection for the bones, and to acquire protective amounts of all the nutrients that can be stored.

Athletes can take this "low body fat in the name of improved performance" idea too far. While the average body fat percent in the United States and Europe is increasing, low body fat percent is clearly a health problem. The female athlete triad of disordered eating and osteoporosis is a relatively new phenomenon. Women athletes who strive for better performance and lower body weight, often find themselves caught in a negative spiral that actually leads to decreased performance and health risks; eating disorders require special attention and professional assistance. How Much Is Too Much?

Just as too little body fat can create devastating physiological complications, too much body fat can have equally harmful effects. Obesity is a condition in which a person is overfat or has an axcess of adipose tissue. Negative health consequences of obesity become active for males with body fat percentage greater that 25% and for females with body fat exceeding 32%. In fact, body composition has been used more and more to make future predictions about health and disease in individuals. Health Risks Associated With Too Much Body Fat :

increased blood pressure increased total cholesterol level increased LDL (bad) cholesterol increased risk of cardiac problems increased risk of Diabetes hardening of the arteries aggravation of osteoarthritis promotes blood clots and varicose veins GI disorders increased predisposition to some cancers decreased reaction time reduced balance and coordination increased susceptibility to infections decreased circulation delayed wound healing

While some aspects of your body composition are based on heredity (such as where you tend to store excess fat), for the majority of the population Percent Body Fat is related to lifestyle. After about age 16, changes in body fat are due to changes in fat cell size not number. These cells expand (or shrink) to accommodate excess calorie storage. However, you can make dramatic changes in your body composition. To increase or decrease your percent of bodyfat, you need to create the right balance between the calories you consume and the calories you burn. The most effective way to do this is to decrease your consumption of fat and increase your activity level. Aerobic exercise is a very effective way to decrease body fat, however, you must combine strength training in order to maintain or gain muscle mass and tone. If you haven't been active, you may want to begin with 15 minutes of exercise and gradually increase. If you are beginning a new exercise program, you are advised to first consult your physician.

Source: American College of Sports Medicine