No. Fat-free mass includes water, bone, organs and other non-fat tissues as well as muscle. A change in this number does not prove an equal change in muscle.
Know what each number means
Understand Your Body Composition
Body weight, body fat and lean mass answer different questions. Choose a metric for the decision you need to make.
Separate the terms
Body weight is total mass. Fat mass is the estimated mass of body fat. Fat-free mass includes everything else, including water, bone and muscle; it is not a synonym for skeletal muscle.
- Body-fat percentage = fat mass ÷ body weight × 100.
- At 80 kg and an estimated 20% body fat, estimated fat mass is 16 kg and fat-free mass is 64 kg.
- An uncertain body-fat estimate makes both derived mass estimates uncertain.
Choose your next question
Follow the method-specific guide instead of comparing unlike measurements.
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