What is lean muscle mass?

Everyone carries fat around on their bodies. Recent studies have suggested that any fat cells you obtain before you are 20 years old are with you for the rest of your life (remember that young people the next time you put that ice cream in your mouth). Fat cells are highly elastic, so fortunately for those of us who decided to bring a few fat cells along for the ride after age 20, they can be shrunk really really really small to the point where they are basically cells without fat in them.
 

Everyone has a specific amount of fat (approx 2-5% for men and 10-13% for women due to child bearing and hormonal differences) that is essential. This is the fat that is padding your organs, used in metabolic operations, etc… The science doesn’t matter, what matters is that those numbers are your lowest possible threshold. For a boxer, any fat they are carrying above and beyond the minimum essential amount is stealing weight that could be replaced by muscle that makes them more effective in the ring.That is one very big reason why boxer’s physiques are so ripped. They are trying to jam as much muscle as possible into their weight category and to do that something has to disappear – fat.
 

Another important reason to want to increase lean body mass is because muscle eats fat. You don’t have to look like a bodybuilder, but adding some extra muscle will allow you to eat more if you wish and still maintain your weight. More muscle will give you better fine tune control over the amount of fat on your body.
 
Therefore, it really doesn’t matter what your bathroom scale tells you. What you really want to be concerned about is lean body mass.