Body Composition vs. Body Fat

Body Composition is the technical term used to describe the different components that, when taken together, make up a person’s body weight.

Body Tissues
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.

Because scales can’t determine the lean-to-fat ratio of that weight, an individual can be “over-weight” but 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.

There are several different methods of assessing the percent of fat vs. lean mass of an individual. These methods are referred to as Body Composition Analysis.

The gold standard of body composition analysis is hydrostatic or hydrodensitometry. Although, because it is time-consuming, cumbersome, and complicated, most physiologists turn to skinfold measurements, as an acceptable alternative means of assessment. The ACSM states that skinfold measures, when performed by a trained, skilled tester, are up to 98% accurate. Practical assessment of body composition explains in detail how one should perform a proper analysis. Bio impedance is another, highly controversial method of assessing body fat percentage.

What should your body fat percent be?
A better question might be, “What is your ideal weight? Body fat percent varies considerably for men and women, and with age. 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 body fat is closer to 15%-18% for men and 22%-25% for women.

Typically, athletes find themselves at the low end of this scale. Optimal levels of body fat are much lower for those striving for a high level of 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 bodyfat 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 explain why a lot of those defensive linemen appear to have 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% body fat.

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. Female 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.

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.

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, 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.

Can I Change My Body Composition?
Yes. To increase or decrease your percent of body fat 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.


About the Author

Elizabeth Quinn, M.S., is an exercise physiologist and health information writer and researcher. She currently manages the clinical health information development for a NW health care organization.


Elizabeth has worked as an exercise physiologist in sports medicine clinics, corporate wellness facilities and rehabilitation clinics. A former national silver medalist in road and track cycling, Elizabeth continues to participate in recreational cycling, mountain biking, running, skiing and almost anything else that requires movement.


Elizabeth has a master’s in exercise science and bachelor’s in psychology. In addition, she has worked as an ACE certified Personal Trainer, and a professional member of ACSM.

From Elizabeth Quinn:

“Sports Medicine has a reputation of being reserved for professional athletes, but anyone who is active can benefit from understanding the basics of sports medicine.”