Body composition is used to describe the proportion of body fat to fat-free mass. Whether using circumference measurements, calipers, or water-displacement tests to determine percentage of body fat, total body composition equals 100 percent. That is, fat-free mass is equal to body composition minus body fat. Exercise and nutrition are key to improving the percentage of muscle mass in relation to body fat.
Estimating Body Fat
Body fat can be measured most accurately by water displacement; however, it requires a water tank and costs are similar to medical tests in an outpatient lab. A free, simple method uses calipers to measure skin-fold thickness at various anatomical sites. The measures are totaled and compared against gender and age norms. The percentiles are then described as "average," "below average," "above average," and "well above average." For example, a 38-year-old woman with 24-percent fat is "average," in the 50th percentile.
Fat-Free Mass
The percentage of the body that is not fat is actually comprised of muscle, bone, water, lymph, blood, and intestinal contents. All together, this is called "fat-free mass." For example, the 38-year-old woman with 24-percent fat has 76-percent fat-free mass. Muscle percentages are lower than fat-free mass, so most athletes concentrate on body fat to guide them in body composition. The lower the body fat, while maintaining total body mass, the leaner the physique.
Women
Women naturally have more fat than men. American women who are considered to be of an athletic body composition range from 18- to 23-percent body fat. Adolescent girls need to maintain essential body fat to ensure normal development of bones and onset of menstruation. The "female athlete triad" is the name of a syndrome involving abnormal eating, bone density, and menstruation patterns. Coaches and parents need to be aware of this syndrome; it is common in high school and college-level athletics.
Men
Men are genetically predisposed to carrying much less fat than women. Essential fat for a man is around 4 percent, and an athletic man has body fat that ranges from 8 to 15 percent. Bodybuilders can attain 2- to 3-percent body fat for a competition, but generally this is only for a matter of a day or two, as it is not sustainable. "Off-season" bodybuilders will go back to 8-percent body fat, as they need to have enough energy to lift weights, and a metabolism that will allow them to add muscle.
Aging
Both men and women lose muscle mass and bone density starting in middle age. Combined with a sedentary lifestyle, fat-mass gains combine with the loss of muscle to change body composition to a higher fat percentage. According to the American College of Sports Medicine, exercise can reverse this trend and bring body-fat levels back down to improve health.
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