Lean body mass (LBM) is often thought to be defined as muscle, but it includes much more then that. Lean body mass is an accumulation of everything in the body except fat. This includes muscles, bones, organs, skin and functional elements such as water and cells. High amounts of lean body mass affect the body's ability to control weight, absorb protein and function on a daily basis. LBM is determined by your body fat percentage and your overall weight.
Importance
LBM is a key concept to understand when your goal is to loose weight and decrease body fat. It helps define your body's resting metabolic rate or the number of calories your body is able to burn per day while at rest. As your LBM goes up, so does the number of calories you burn at rest. Other positive associations include lower risk factors for high blood pressure and cholesterol, heart disease and certain types of cancer.
Calculating Lean Body Mass
The first step in finding your LBM is to find your body fat percentage. This will allow professionals to categorize the amount of fat you have in your body, which will help them find your lean body mass. There are many different techniques for calculating this, and many are more accurate then others.
Measurement Methods
A simple technique that uses basic measurements to find body fat percentage is a predictive body fat percentage table based on an individual's body mass index. This method is not considered accurate because of the disassociation that is often found between a person's weight and his actual body fat. Taking skin fold measurements using skin calipers is another method. This is a good technique because most health and fitness professionals are trained in using skin calipers. The method is quick and fairly accurate. The American College of Sports Medicine's (ACSM) guidelines show the accuracy to be plus or minus 3.5%.
Measuring Body Volume
Another way of measuring body fat is by estimating whole body density using the ratio of body mass to body volume. One technique is called hydrostatic weighing and is done by weighing an individual in water and calculating the water displacement to create a body density ratio. This standard method but requires scientific equipment and precise measurements that are often hard to calculate with anxious clients. The same technique used in hydrostatic weighing can now be used to find body volume using air displacement instead. In this method, an individual is put inside a small pressure chamber where changes in pressure are measured to find body volume. ACSM now claims that this technique is just as accurate as hydrostatic weighing and is much less stressful for the client.
Equation
Once you have found your body fat percentage, you can then calculate your lean body mass. First, you must find your body fat in pounds by multiplying your whole body weight by your body fat percentage in decimal form. Then take your whole body weight and subtract your body fat in pounds. The remaining number is your lean body mass.
References
- "ACSM's Guidelines for Exercise Testing and Prescription"; The American College of Sports Medicine; 2006
- Long Term Wellness Solutions: Lean Body Mass
- Brian Mac Sports Coach: Body Fat Percentage
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