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What is a body composition test?

A body composition test measures a person’s body-fat  percentage.  Body composition refers to the relative percentage of body weight that is fat versus fat-free mass. Fat-free mass can be defined as body weight except stored fat, and includes muscles, bones, water, connective and organ tissues, and teeth, whereas fat mass includes both essential fat (crucial for normal body functioning) and nonessential fat (storage fat or adipose tissue). Example body composition tests include skinfold tests, bioelectrical impedance, and hydrostastic (underwater) weighing.

Body composition tests measure your body fat and your lean tissue for a more accurate picture of health than weight alone. There are a number of methods of testing that range in ease and in accuracy. The most common methods until recently have been skinfold measurements and bioelectrical impedance, which both can be done within minutes. Skinfold measurements are most accurate when the same tester does both a pre and post assessment, and has significant experience performing the tests. The gold-standard of body composition has traditionally been underwater weighing, usually available in university or clinical settings. A dexa scan used for bone density testing can also measure body composition.

Recent methods of assessing body composition by scales that also measure body fat have made it accessible to track your body composition at home. 

A few things to keep in mind if you're testing body composition:
  • Hydrate well before you test
  • Don't exercise before a test
  • Test at the same time of day to most accurately compare
  • If you're female, test at the same time of month each time you test
  • It takes 6-8 weeks to see a significant change of 3-5%, so be patient

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.