Lean Body Mass vs Muscle Mass

Consider the following three statements:

  • “I’m not working out to get huge; I just want to build strength and put on five pounds of lean muscle.”

  • “My goal is to workout more and put on a healthy five pounds of muscle mass before next season.”

  • “I’m going to add more protein to my diet and hopefully gain 5 pounds of lean body mass by the end of the month.”

In each one, someone wants to gain five pounds of something but is using three different terms. Are these three ways of saying the same thing? Can they be used interchangeably? Or are they different?

"Lean" refers to the absence of body fat. In truth, all muscle is lean muscle. There are three major muscle types – cardiac, smooth, and skeletal – skeletal muscle mass is the only type of muscle that you can actively grow and develop through proper exercise and nutrition.


Lean Body Mass (LBM) = Total Weight – Fat Mass

LBM includes the weight of:

  • Organs

  • Skin

  • Bones

  • Body Water

  • Muscle Mas

Lean Body Mass correctly uses the word “lean” as it describes the entire weight of your body minus fat. This is why it is also known as “Fat-Free Mass.”


When people talk about gaining muscle by eating more protein or muscle building workouts, what they’re really talking about is gaining or building their Skeletal Muscle Mass (SMM).


Muscle gains definitely contribute to LBM gains, but so does water, which can fluctuate throughout the day depending on hydration status, diet, and physical activity.

It’s also important to note that muscle itself contains water – a lot of it. Muscle can contain up to 79% water content. Research has also shown that resistance training promotes the increase of intracellular water in both men and women.

There is only one way to calculate what is happening to your Lean Body Mass: getting your body composition analyzed with the InBody scale


. Without testing your body composition, there will be no way to know what any gain or loss in your body weight is due to.

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