In October I was lucky enough to be invited to present at the great lakes regional meeting of the national strength and conditioning association. This was fun and I got to talk about doing body comp tracking with athletes and how you can use this data to help you program with your athletes more effectively and to help them be more successful. There were a few special situations with changes in lean body mass that I wanted to bring up that honestly I ran out of time to get in to. First I will give some basics on body composition.
Two compartment model
This is where the body is divided in to lean mass and fat mass. This is a simple divide and inside of the fat mass you have not only the fat that makes you feel self-conscious on occasion, but you have your bone marrow and nervous system which are both mostly made up of fat. On the lean mass side you have not only your muscle mass, but most of your internal organs, skin, bone (sometimes separated in the three compartment model), connective tissue, and even things like your hair. Since there are so many things that go in to each bucket it is important to know a few special situations with changes in lean mass and fat mass
Massive weight loss
Folks that lose a considerable amount of fat mass tend to have extra skin that with time tends to shrink down. This on a body comp scan could freak out your client or athlete since they think they are losing their lean mass when in reality muscle mass can go unaffected while their skin component decreases.
Atrophy and hypertrophy of your GI
Literally when you calorie restrict for longer periods or eat much heavier for a periods of time you change the size of your intestines (GI for short). This shows up as lean mass during any body comp scans. Part of that lean mass lost when you aren’t eating as much is due to your GI actually shrinking a bit and the antithesis is true when gaining weight. This is why having limb lean mass is important because you can truly tell if your muscles are getting bigger or smaller since those don’t have other organs inside them that will change in size.
Body Hair changes
For the other incredibly hairy guys out there, your hair is part of lean mass. So if you cut your super long hair or remove your large amount of body hair that will count as lean mass loss. Yes you don’t think about this too much, but if you lost half a pound of lean mass through hair loss and you think this is muscle mass change this will throw you off.
There are a few subtle ways that you can lose or gain lean mass that isn’t the muscle mass that people are really going for. Make sure that when you are tracking you need to use multiple methods and be sure the changes you are seeing are the ones you truly want to occur. I hope this helps and if you have any questions please let me know.