Your fat-free mass includes your muscles, organs, bones, and connective tissue. It also includes water weight. In other words, this is what would be left if you removed every single fat cell from your body. Muscle mass is a major component of your fat-free mass, and it should weigh more than your fat mass. Furthermore, muscle mass has a huge positive impact on your metabolism or "metabolic rate" which is how many calories your body burns for energy. The more muscle mass you have, the more calories you burn, even when you're not exercising. Advanced GlucaPro