Fat-Free Body Mass Benefits

what is fat free mass
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Fat-free mass is one of two human body components: Fat, and everything else. Fat-free mass (FFM) includes internal organs, bone, muscle, water, and connective tissue. Different methods are used to estimate your body composition, or your ratio of fat mass to fat-free mass.

When you get your body composition measured, you get an estimate of your body's fat mass. For example, your estimated body fat may be 24%. But have you ever wondered what makes up the other 76%? Fat-free body mass includes most of your body's vital tissues and cells. That means: 

  • Organs: Internal organs such as your heart, brain, and liver
  • Muscle: Cardiac muscle, smooth muscle, and skeletal muscle
  • Bone: The bones that protect you and provide your body's structure
  • Connective tissue: Tendons and ligaments that connect bones and muscle
  • Water: Approximately 50% to 75% of your body

Fat-free mass is a phrase used to describe all of the tissues in your body that are not adipose (fat) tissue.

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% to 5% body fat for essential functions, but women need more. A woman's body fat should range between 10% and 13% for proper functioning. 
  • Non-essential fat: Fat that is not needed for essential functions is called excess 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 increase important fat-free mass like muscle and bone. Most of us have a body fat percentage that is much higher than what we need. Being overweight or obese increases the risk for medical conditions such as 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.

  • Improved metabolism: Muscle tissue burns more calories than fat mass. So if you increase the amount of muscle, you boost your metabolism and burn more calories all day long.
  • Improved strength: When you increase muscle mass, you improve your body's strength. For example, stronger arms are better able to lift heavy grocery bags or carry bulky luggage.
  • Improved appearance: Fat-free muscle mass helps to shape a tighter body. When you replace fat mass with fat-free mass, your body looks healthy and lean.
  • Increased daily movement: Muscles that are strong and flexible move more comfortably through activities of daily living. When you move more efficiently, it's easier to stay active all day long.

How to Improve Body Composition

So how do you build muscle to change your body's ratio of fat mass and fat-free mass? Resistance training is key. Start a strength training program that includes weight lifting or bodyweight exercises to build muscle and improve strength. You can 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, 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 body composition, decrease fat, and improve your body's fat-free mass.

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Article Sources
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  1. American Council on Exercise. Percent body fat calculator: Skinfold method.

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Health risks of being overweight. Updated February 2015.