Measurement of the human body is known as anthropometry. Anthropometic evaluation for body weight and/or composition of clients is a frequent occurrence for professionals in the health and fitness industry. These calculations are used to establish baseline numbers for clients, to set desired goals for weight loss or gain for an individual, and to gauge a person's pre-disposition 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 an individual's total mass, 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.
Calculations/BMI
BMI techniques assess body weight relative to height. It compares a person's weight in kilograms divided by their height in meters squared. The formula looks like this: Weight (kg) / Height (m2). Converting body weight from pounds to kilograms involves dividing body weight by 2.2. For example, a 150 lb. individual weighs approximately 68 kg (150 divided by 2.2 = 68). Height in meters is determined by converting inches (in) into centimeters (cm) and dividing the result by 100. 1 in. is equal to 2.54 cm. Thus, a person who is 6 ft. tall is 72 inches. 72 x 2.54 = 183 cm. 183/100 = 1.83 m.
Calculations/Body Fat
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 in. at the skinfold site. Then, the contact surface of the caliper is attached to the grasped area of the body for reading. There are 9 possible sites for anatomical measurements. However, 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. The four-site Durnan Formula is the easiest since it involves determining the sum of the four locations in centimeters and comparing the result with the age of the participant.
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.
The following is a classification list of body fat percentages for men and women, respectively:
Essential fat: 2 to 4 percent vs 10 to 12 percent.
Fitness: 14 to 17 percent vs. 21 to 24 percent.
Average (acceptable): 18 to 25 percent vs. 25 to 31 percent.
Obese: 25 percent vs. 32 percent.
Considerations
Determining BMI can reasonably be done by anyone able to determine 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.
- "NSCA's Essentials of Personal Training," Roger Earle and Thomas Baechle; 2004.
Member Comments