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Body Composition. Body Composition. Definition: describes the percentages of fat, bone, muscle, and fluid that make up body weight. Because muscular tissue takes up less space in our body than fat tissue, our body composition, as well as our weight, determines leanness.
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Body Composition • Definition: describes the percentages of fat, bone, muscle, and fluid that make up body weight. • Because muscular tissue takes up less space in our body than fat tissue, our body composition, as well as our weight, determines leanness. • Factors that affect a person’s body composition may include: heredity, diet, exercise, occupation.
Two people at the same height and same body weight may look completely different from each other because they have a different body composition.
Male and Female • The National Institute of Health recommends that a healthy adult male's body should have between 13 and 17 percent fat. • A healthy female's body should be composed of between 20 and 25 percent fat. • FITNESSGRAM suggest that there is an optimal range within the HFZ. Ideally, students should strive to be within the optimal range, which is 10% to 20% fat for boys, and 15% to 25% fat for girls. • Why is the FitnessGram different than that of an adult? Answer: kids are still growing. • Levels significantly above these amounts may indicate excess body fat.
Body composition (particularly body fat percentage) can be measured in several ways. • Skinfold measures • Bioelectrical Impedance • Underwater Weighing • Body Mass Index (BMI)
Skinfold Measurement • Description: This method is the most widely used body composition testing method for assessing percent body fat. Equipment used for this assessment includes a skinfold caliper. A Skinfold Caliper is designed specifically for simple accurate measurement of subcutaneous tissue. Either a 7 or 3 site skinfold may be assessed.
Advantages: Easy to use once skill has been mastered Does not require much time Noninvasive method Inexpensive way of estimating percent body fat Disadvantages: Technical sources of error Mostly concerned with subcutaneous fat (under the skin) May not be an ideal measurement for those who are obese and very lean Advantages and Disadvantages
Bioelectric Impedance • Description: By standing barefoot on metal foot plates, an undetectably low voltage electric current is sent up one leg and down the other. Since fat is a very poor conductor of electricity, a lot of fat will impede the current more so than a lot of lean tissue. By measuring the resistance to the current, the machine estimates the percent body fat.
Advantages: Requires little or no technical knowledge of the operator or the client Testing itself takes less than a minute The unit can be easily transported from place to place Requires only an electrical outlet and the machine itself Disadvantages: This method has a higher standard error range than most people desire Tends to consistently overestimate lean people and underestimate obese people Advantages vs. Disadvantages
Underwater WeighingA.K.A. Hydrostatic Weighing • Description: This method uses Archimedes principle which states that when a body is submerged in water, there is a buoyant counter force equal to the weight of the water which is displaced. Because bone and muscle are more dense than water, a person with a larger percentage of fat free mass will weigh more in the water and have a lower percent body fat. Conversely, fat floats. Therefore, a large amount of fat mass will make the body lighter in the water and have a higher percent body fat.
Advantages: This method is currently considered the "gold standard" in percent body fat measurement Repeat measures usually prove consistent, and can be used to chart progress Disadvantages: This method usually requires a lot of equipment and space Testing is time consuming and involved Requires in-depth knowledge to administer the tests and compute the calculations Being submerged under water may be difficult and produce anxiety for some How accurate is it?If each test is performed correctly according to the recommended guidelines, there is a +/- 1.5% error. (Note: Accuracy depends on the client’s ability to blow all the air out of their lungs both during a pre-test screening with a spirometer, and during the test itself. Since air makes the body float, inability to perform either of these maneuvers will result in miscalculation of the percent body fat.)
Body Mass Index (BMI) • Provides an indication of the appropriateness of a child’s weight relative to height. • Body mass index is determined by the following formula: weight (kg) / height squared (m) • Example: a student weighing 100lbs (45.36 kilograms) who is 5 feet (1.52 meters) tall would have a BMI of 19.6. Another student of the same weight but 5 feet 2 inches tall would have a BMI of 18.3.
Advantage Fast Does not require much skill Procedure is less invasive than skinfold testing and may be better accepted in some districts. Disadvantage Estimates based on height and weight such as BMI result in 5% to 6% error because body weight reflects muscle and bone mass and not just fat mass. Body mass index is not the recommended procedure for determining body composition because it does not estimate the percent of fat. It merely provides information on the appropriateness of the weight relative to the height. BMI
Good Body Composition • Decrease levels of body fat that cause obesity • Decrease risk of coronary heart disease • Decrease chances for stroke • Decrease chances for diabetes • Lower blood pressure • Lower Cholesterol levels
Lifetime • Like other dimensions of health-related fitness, body composition does affect health status (even in childhood) and does improve with regular participation in physical activity and diet.
