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) is that "everything else," from organs, to water to connective tissue. The term "body composition" describes the ratio of fat mass to fat-free mass, and it can be measured using a few different methods.

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 the term used to describe all of the tissues in your body that are not adipose (fat) tissue.

Fat Mass and Fat-Free Mass

Body fat, also called adipose tissue 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. There's not much you can do to significantly change the amount of organ tissue or bone in your body. But you can try to build muscle. Doing so has many benefits.

  • Improved metabolism: Muscle tissue burns more calories than fat mass. So if you increase the amount of muscle you have, you boost your metabolism and burn more calories all day long.
  • Improved strength: When you increase muscle mass, you improve your body's strength. 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.

Increasing your fat-free body mass can be helpful for weight management. Research shows that fat-free mass plays both an active and passive role in the body's energy intake and requirements.

How to Measure Body Composition

You can determine your fat-free body mass and overall body composition using a few different methods.

  • Skinfold measurements are a popular method of determining body fat percentage. Calipers take measurements from specific parts of your body, which are used in a calculation to translate them into a percentage of body fat.
  • Bioelectrical impedance analysis is performed using specialized scales or handheld devices that send an electrical current through your body to determine fat-free mass.
  • Progress photographs are a less accurate, but easier method of tracking your fat-free mass. While they can't provide you with numbers, progress photos can show you how your body is changing.

How to Improve Body Composition

If you'd like to change your body composition, improving fat-free mass and reducing body fat, you'll likely need to make changes in your exercise routine and diet.

Resistance Training

You can improve your fat-free mass by building muscle. Start a strength training program that includes weight lifting or bodyweight exercises to build muscle and improve strength. You can work on resistance training on your own, at home, without expensive equipment, trainers, or gym memberships.

Dietary Protein

Getting an optimal amount of protein for your needs will help increase lean mass and prevent muscle loss. This amount will depend on your body weight, current lean mass percentage, age, sex, and activity. Protein helps with muscle building and meal satiation, keeping you full longer since it takes more time to digest.

A Word From Verywell

If you're ready to begin your own program at home or the gym, make sure you are healthy enough for exercise. Then start slowly to avoid injury or burnout. Include a healthy amount of protein for your body to support your lean mass development. Before you know it, you'll build muscle, improve body composition, decrease fat, and improve your body's fat-free mass.

4 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  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.

  3. Dulloo AG, Jacquet J, Miles-Chan JL, Schutz Y. Passive and active roles of fat-free mass in the control of energy intake and body composition regulation. Eur J Clin Nutr. 2017;71(3):353-357. doi:10.1038/ejcn.2016.256

  4. Carbone JW, Pasiakos SM. Dietary protein and muscle mass: Translating science to application and health benefitNutrients. 2019;11(5):1136. doi:10.3390/nu11051136

By Rachel MacPherson, BA, CPT
Rachel MacPherson is a health writer, certified personal trainer, and exercise nutrition coach based in Montreal.