There are many methods of assessing a person's fat and lean mass. The most common methods include:
Underwater/Hydrostatic Weighing: This method of determining body composition relies on fat tissue and its density. Since Fat tissue is less dense than water, a person with more body fat will weigh less underwater and be more buoyant. Underwater weighing has been considered the gold standard for body composition assessment; however it is very costly and typically only found in university and medical settings for research purposes. (*not offered at Campus Recreation)
Skinfold Thickness Measurements: Fitness Centers use simple skinfold measurements to determine body fat percentage. The American College of Sports Medicine says that when performed by a trained, skilled, tester, they are up to 98% accurate. Measurement can use from 3 to 9 different standard anatomical sites around the body. The tester pinches the skin at the appropriate site to raise a double layer of skin and the underlying adipose tissue, but not the muscle. The calipers are then applied at right angles to the pinch and a reading is taken two seconds later.
Bioelectrical Impedance: Bioelectrical impedance measures the resistance of body tissues to the flow of a small, harmless electrical signal. The proportion of body fat can be calculated as the current flows more easily through the parts of the body that are composed mostly of water (such as blood, urine, and muscle) than it does through bone, fat, or air. It is possible to predict how much body fat a person has by combining the bioelectric impendence measure with other factors such as height, weight, gender, fitness level, and age.
BMI - Body Mass Index: BMI is calculated by taking a person's weight and dividing by their height squared. The higher the figure, the more overweight you are. Like any of these types of measures it is only an indication and other factors such as body type and shape have a bearing as well. Remember, BMI is just a guide - it does not accurately apply to elderly populations, pregnant women or very muscular athletes such as weightlifters.