Anthropometry is the measurement of the human body. Anthropometric evaluations for body weight or body composition of clients are routinely performed by fitness professionals. These calculations are used to establish baseline numbers for clients, set desired goals for weight loss or gain for an individual and gauge a person's predisposition to many illnesses or diseases based on body composition. Body Mass Index, or BMI, and body fat percentages, also called skinfold testing, are two inexpensive methods of determining body composition.
Function
The BMI is used to calculate the total mass of an individual, regardless of the type of tissue being measured. In other words, it does not distinguish between bone tissue weight, fat tissue or muscle tissue. Conversely, body fat percentage pinpoints fat mass from fat-free mass or what is known as lean body mass--bone, muscle and organs.
Classifications
According to the National Institutes of Health, the classification for BMI are underweight, which is less than 18.5; normal, between 18.5 and 24.9; overweight, between 25.0 and 29.9; obesity I, between 30.0 and 34.9; obesity II, between 35.0 and 39.9; and obesity III, greater than or equal to 40. These guidelines are inclusive for both men and women. However, guidelines for body fat percentage is gender specific. For example, essential body fat levels are 2 to 4 percent for men and 10 to 12 percent for women. Ideal percentages for fit individuals are 14 to 17 percent for men and 21 to 24 percent for women. Average or acceptable percentages are 18 to 25 percent and 25 to 31 percent for men and women, respectively. A classification of obesity is at or above 25 percent body fat for men and 32 percent for women.
Calculations
Essentially, the BMI is a calculation of a person's weight in kilograms, divided by the square of his height in meters. Body fat or skinfold measurements are evaluated via skinfold calipers. The objective is to use one hand to separate fat tissue from lean tissue by using the thumb and index finger to grasp approximately 3 inches at the skinfold site. The contact surface of the caliper is attached to the grasped area of the body for reading. Although there are nine possible sites for calculation, the formulas used to input measurements are based on three-, four- or seven-site calculations. The following are the areas used for skinfold calculations: abdominals, triceps, biceps, chest, midaxillary, subscapular, calf, suprailium and thigh.
Theories
It is believed that the calculation and corresponding guidelines of determining the BMI can gauge an individual's predisposition to certain medical issues. For instance, females with a BMI lower than the average range are considered underweight and may show signs of anorexia nervosa, which could lead to myriad health problems, such as amenorrhea. Conversely, men or women who fall into the obese categories are at increased risk of developing diabetes or heart-related conditions.
Considerations
Determining BMI can reasonably be done by anyone able to calculate the necessary values for body weight and height. However, body fat testing should be done by a trained professional to ensure accuracy. Also, time of day, hydration status and previous meal consumption could influence both BMI and body fat calculations. It is ideal to test at the same time of day, preferably first thing in the morning.
References
- "ACSM's Health-Related Physical Fitness Assessment Manual," American College of Sports Medicine; 2005.
- National Institutes of Health: Body Mass Index Table and BMI Calculator
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