I’ve been getting a lot of questions recently about “Lean Body Mass”, so I thought it would be a good idea to address the concept in more depth so you can understand exactly what it is, why it’s important, and how to calculate it.
Simply put, lean body mass is comprised of everything in your body besides body fat.1 Your lean body mass includes:
…and anything else in our bodies that has mass and is not fat.
As an aside, for the average adult male about 42% of body weight is skeletal muscle and it’s about 35% for females.
Lean Body Mass = Body Weight – (Body Weight x Body Fat %)
This equation is taking your body weight in pounds and subtracting it from the amount of fat you have in your body in terms of pounds. Simple. If you don’t know how to measure your body fat, here are 5 Ways to Measure Body Fat.
Beware of some of the calculators online that attempt to arrive at your lean body mass without knowing your body fat percentage first. These calculators attempt to calculate your lean body mass based on your height, weight, age, and/or sex, which will most likely be completely inaccurate.
Most people rely 100% on the weight scale when attempting to track changes in body fat. While I do strongly recommend Monday Morning Weigh Ins during a fat loss program (and even after) as a proxy for fat loss, tracking body fat directly and tracking LBM is helpful to make sure you are losing only fat and no muscle. Losing muscle is highly undesirable because your metabolism will decrease and aesthetically, you may not look leaner even if you do lose weight.
Lean body mass is also your set point to determine how much fat you should lose and what your body fat percentage will be if you lose a certain amount of fat. You can check out the Ideal Body Weight Formula, which takes into account your lean body mass to arrive at your ideal weight.
If you would like to learn more about losing fat without losing muscle, I highly recommend checking out my free Get Lean Guide.
I hope this was helpful. Let me know if you have any questions, or have anything to add by leaving a comment.