What Is Fat-Free Mass?

Learn the Difference Between Fat Mass and Fat-Free Body Mass

what is fat free mass
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Fat-free mass is one of two human body components. Fat-free mass (FFM) includes internal organs, bone, muscle, water and connective tissue. Fat-free mass differs from fat mass. Different methods are used to estimate your percentage of fat mass and fat-free mass.

Example: Fat-free mass can refer to any body tissue that does not contain fat.

What Is Fat-Free Mass?

When you get your body composition measured, you got an estimate of your body's fat mass.

For example, your estimated body fat may be 24 percent. But have you ever wondered what makes up the other 76 percent?  Everything in your body that is not body fat is fat-free mass.

Fat-free body mass includes most of your body's vital tissues and cells. 

  • Organs. Internal organs such as your heart, brain and liver are examples of fat-free mass.
  • Muscle. Cardiac muscle, smooth muscle, and skeletal muscle are examples of fat-free mass. Skeletal muscles contract to produce movement in your body and perform other essential duties.
  • Bone. The bones that protect your body and provide your body's structure are fat-free body mass.
  • Connective tissue. Tendons and ligaments that connect your body's bones and muscle are examples of fat-free mass
  • Water. Approximately 50-75 percent of your body is water. Water is free from fat and can be considered fat free mass.

Fat Mass and Fat-Free Mass

What is not included in your body's fat-free mass?

Adipose tissue, or fat.  Body fat or fat mass can be divided into two categories.

  • Essential fat. Your body needs a certain amount of fat to function properly. Men need 2-5 percent body fat for essential functions but women need more. A woman's body fat should range between 10-13 percent for proper functioning. 
  • Non-essential fat.  Fat that is not needed for essential functions is called excess fat or non-essential fat. This fat provides insulation and protects vital organs.

If you're trying to lose weight, you should try to decrease fat mass and maintain or improve important fat-free mass like muscle and bone. Most of us have a body fat percent that is much higher than what we need. When our bodies carry too much fat, we become overweight or obese. Being overweight or obese can put you at higher risk for certain medical conditions like heart disease, metabolic syndrome, high blood pressure or type 2 diabetes.

Benefits of Improving Fat-Free Mass

If you follow healthy lifestyle habits, eat a nutritious diet, and get plenty of exercise, you can protect your organs and build strong bones. But there's not much you can do to significantly change the amount of organ tissue or bone in your body.

You can, however, improve your fat-free mass by building muscle. Increasing fat-free muscle tissue provides several benefits.

How to Improve Fat-Free Mass

So how do you build muscle to change your body's ratio of fat mass and fat-free mass?

Resistance training is the key. You can start a strength training program that includes weight lifting or body weight exercises to build muscle and improve strength. You can even change your body without expensive equipment trainers or gym memberships.

If you're ready to begin your own program at home or at the gym, use smart resources—like the guides at Verywell— to get started. You should also make sure you are healthy enough for exercise. Then start slowly to avoid injury or burnout. Before you know it, you'll build muscle, improve your body composition, decrease fat, and improve your body's fat-free mass.

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