Lean Body Mass vs. Skeletal Muscle Mass

Lean Body Mass (LBM) and Skeletal Muscle Mass (SMM) ... we hear these two terms used interchangeably without much thought as to what each really means.

Let’s clarify.

LBM = total weight of organs/skin/blood/bones/body water and SMM.

SMM = muscle only.

An increase in SMM will result in an increase in LBM, but the opposite isn’t necessarily true.

When LBM increases we can be fairly certain our bones, skin and organs are not gaining any appreciable weight. So this leaves changes in either SMM or total body water (or both). Depending on factors such as hormonal changes, diet, activity/exercise, hydration status and even sleep, body water can fluctuate (upwards of 5-6 lbs daily) and thus change LBM (without changing SMM).

(As a side note, losing body water also doesn’t mean you’ve lost SMM.)

Understanding that SMM is a component of LBM, we need to be laser focused on preserving SMM as we age.

If we’re interested in living a long and healthy life and doing all the activities we’d like to do whenever we want to do them, we need to be strong.

Let me be even more blunt …

WE NEED TO FIGHT LIKE HELL TO HANG ON TO AS MUCH MUSCLE AS POSSIBLE FOR AS LONG AS POSSIBLE.

And this means strength training MUST be a priority.

If you’re already strength training, keep it going and continue to get out of your comfort zone to push skeletal muscle mass to maintain or even grow.

If you’ve never strength trained (maybe you’re intimidated to even start?), push those fears aside and get a program going immediately. It’s never too late!

And if you have no idea where to start, well, you can start with an assessment and program design from Functional Elements (it’s what we do).

This assessment will provide you with two very important things:

1) Baseline data on your body, which is an invaluable starting point. And yes, this baseline data includes your LBM and SMM levels.

2) A program and strength training game plan built for your body and goals. Even if you plan on training on your own, having this road map to follow will help cut the biggest fear that most who don’t strength train have - uncertainty.

I’ll leave you with this quote, which in my opinion says so much:

“If you have the aspiration of kicking ass when you’re 85, you can’t afford to be average when you’re 50.”

-Dr. Peter Attia

EAT WITH A PURPOSE - AND BE WELL!

Jaime Rothermich
RD, CSSD, LD, PPSC, CSCS
Functional Elements Training & Nutrition