Body Tissues
The human body is composed of a variety of different tissue types. The so-called 'lean' tissues, which include muscle, bone, and organs, are metabolically active, while adipose, or fat tissue, is not.
Body fat measurement is an important factor in assessing nutritional status and level of general fitness and is much more meaningful than weight alone.
Because a basic scale can't determine the lean-to-fat ratio of your total weight, an individual can be "over-weight" without being "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 such as the Body Mass Index. Therefore, these charts are not a good indication of a person's ideal body weight for optimal health, much less for athletic performance.
The several methods of assessing the percent of fat vs. lean mass of an individual are referred to as Body Composition Analysis.
The procedure of underwater weighing (hysdrostatic or hydrodensitometry) is generally accepted as the standard against which all other methods are compared. But because it is time consuming, cumbersome, and complicated, skinfold measurements is the most common method used. The ACSM states that skinfold measures, when performed by a trained, skilled, tester, are up to 98% accurate.
What should your body fat percent be?
Body fat percent varies considerably for men and women, and age. However, there are some standards. The minimum percent body fat considered safe and acceptable for good health is 5% for men and 12% for women. The average adult body fat is closer to 15%-18% for men and 22%-25% for women. The body fat percents for elite athletes vary largely by sport. The association between low body fat and improved performance is not precise, and there is little evidence of performance benefits when male athletes drop under 8% and women drop under 14% body fat.
You can use percent body fat values to estimate fitness levels as follows:
Unhealthy Low:--------Men <5%-----------Women <12%
Elite Athlete:------------Men 5-7%----------Women 12-14%
Excellent:----------------Men 7-10%--------Women 14-18%
Good:---------------------Men 10-16%-------Women 18-22%
Acceptable:-------------Men 16-19%-------Women 22-26%
Borderline:--------------Men 19-24%-------Women 26-31%
Unhealthy High:-------Men >24%----------Women >32%
How Low Is Too Low?
Athletes can take this “low body fat in the name of improved performance" idea too far. Those who strive for better performance and lower body weight, often find themselves caught in a negative spiral that actually leads to decreased performance and many health risks. While the average body fat percent in the United States and Europe is increasing and causing un-wellness, too little body fat has serious health consequences as well.
How Much Is Too Much?
Just as too little body fat can create some pretty devastating physiological complications, too much body fat can have equally harmful effects. Once men creep up over 24% and women over 32% fat, there is a dramatic correlation with illness and disease.
Isn't Body Composition Genetic?
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, the Body Fat percent 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.
Total Boby Electrical Conductivity or TOBEC
Using the TOBEC method, a person lies in a type of cylinder that generates a very weak magnetic field. The strength of the field is directly related (and depends on) the electrolytes found in the persons body water. Over the course of 10 seconds, the TOBEC makes 10 conductivity readings that estimate lean body mass. From this, a simple equation is used to estimate total body fat. This technique is bases on the fact that lean tissue is a better conductor of electricity than fat (mainly because of the amount of water in lean tissue is much higher than in fat tissue).
The Bio Electrical Impedance system that some bathroom scales offer is based on this concept.