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Lean Body Mass (LBM)
Body Composition
In a nutshell, your body is made up of bones, organs, muscle and fat. Organs, muscle and bones are active mass, while fat is passive mass. A small body fat percentage (3% for men and 11% for women) is necessary for proper functioning of the body. The rest serves as a reservoir for fuel, thermo isolation and a shield against injury. Optimal values range between 5-8% for men and 12-14% for women. Any values higher than that are a sign of excess stored fat.
Fat Measurement
Skin fold body fat measurement is an adequately accurate method, which is also quite user friendly. A device called body fat caliper helps you measure the thickness of skin folds in a few particular places on your body. Results are entered in a formula, together with your age and gender. The final figure is your body fat %.
Normal Weight
The above makes it clear that to calculate the lean body mass of a person you need to subtract the fat weight from the total body mass. However, this is rarely done and most health guidelines only take into account your total body weight. Let’s look at the following examples:
Example
We have two men of the same height. One of them weighs 70 kg and has 5% fat, the other on weighs 90 kg and has 25% fat. Since their bodies will definitely display visual differences the first one might be considered quite thin and the second one relatively strong and tough. It’s easy to calculate that their LBM is almost the same, namely 66.5 and 67.5 kg. Roughly speaking they have the same amount of muscle, but the second one is covered by a generous layer of fat.
Example
We have two women with a height of 165 cm. They weigh 50 and 60 kg and have a body fat % of 20% and 15%. The first one might easily be mistaken for someone who is in good health, while her lean body mass is only 40 kg, which is too little. The second one might be wrongly considered overweight (a sign of poor health), but actually her active weight is 51 kg, which is more than ideal for her height.
In conclusion it is important to remember that total body weight is of little importance compared to lean body mass weight. Lean body mass is what matters, so if you would like to lose weight - lose fat, if you would like to gain weight - gain muscle and thicken your bones.
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