As many of us following the BFL program are using a percentage of body fat as a goal I thought some information on just what comprises this number relevant. What follows is information I have pieced together while researching the subject. At the end of the post I have attached two charts which provide information on BF% goal for men and women at various ages.

[the following is copied from Elizabeth Quinn M.S. article Body Composition Basics at about.com's Sports Medicine site .. and from The Important Role of Body Fat Percentage from how-to-gain-weight.com]

Body Composition

Body Composition is the technical term used to describe the different components that make up a person's body weight. 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.

Body Tissues

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. 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. 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.

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.

The gold standard of body composition analysis is hydrostatic or hydrodensitometry. Although, because it is time consuming, cumbersome, and complicated, and difficult to find, many physiologists turn to other types of measurement as an alternative means of assessment. However, hydrostatic weighing is the method by which all other means of measurement compare their degree of error.

What should your body fat percent be?

Well, this is a loaded question, and the answer reflects the controversy surrounding the issue. A better question might be, "What is your ideal weight? 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 'standards.' The minimum percent body fat considered safe and acceptable for good health is 5% for males and 12% for females. The average adult bodyfat is closer to 15%-18% for men and 22%-25% for women.

Athletes, typically, find themselves at the low end of this scale. Optimal levels of body fat are much lower for those striving for high level performance. Ranges for professional athletes are quite a bit lower than for the average, healthy individual. Much of this difference can be attributed to the increased lean weight (muscle mass) of top athletes. The impact of body size on performance is one consideration that may correlate with body fat.

While levels of body fat seem to be related to performance, body composition alone has never been a great predictor of sports performance. Several studies have suggested that percent body fat is inversely related to maximal aerobic capacity and to distance running performance. Lean muscle mass seems to be positively related to performance in sports where the ability to generate maximal force is required (this may help to explain why a lot of those defensive linemen appear to have a high body fat levels). The body fat percents for elite athletes vary largely by sport. Clearly, 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% bodyfat.

How Low Is Too Low?

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, amenorrhea, 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. There have even been steps taken by the National Collegiate Athletic Association to keep wrestlers from going too far when it comes to 'making weight', or reducing their weight to qualify for a lower wrestling weight class.

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 25% and women over 32% fat, there is a dramatic correlation with illness and disease. 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 Include The Following:

• • 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

Lower is Not Necessarily Better

A certain amount of body fat is vital for the body to function normally and healthily. In fact striving for a body fat percentage that is too low can be dangerous. Here's why:

Measuring your body fat percentage calculates your TOTAL body fat. This total body fat can be split into 2 categories.

Storage Fat -- This consists mainly of fat deposited just under the skin or subcutaneous fat. Storage fat for men and women is fairly similar. For the average man 12% of bodyweight is storage fat and for the average woman 15% of bodyweight is storage fat.

Essential Body Fat -- For the body to function normally and healthily a certain amount of body fat is required. This is called essential fat. For women the average amount of essential fat is 12% of bodyweight and for men it is 3%.

Trying to achieve a body fat percentage that is so low it effects your essential fat stores is NOT good for your health. Some storage fat is also required for good health. Why? It is used to protect internal organs in the chest and abdomen. So aim to stay within the range for age and gender.