Body composition
Also called: body comp scan, fat mass and lean mass measurement
What it means
Body composition is the breakdown of your body into fat mass, lean (muscle) mass, and bone, usually measured by a scan like InBody or DEXA instead of just weighing you on a scale.
Muscle (lean mass) helps keep bones loaded and strong, so tracking it alongside bone density gives a fuller picture of your fracture risk.
Body composition refers to the makeup of your body in terms of fat mass, lean (muscle) mass, and sometimes bone mass. It's usually measured with a scan like InBody or DEXA, which separates your total weight into these different components rather than just giving you one number on a bathroom scale.
For bone health, lean mass matters a lot. Muscle pulls on bone during movement and exercise, and that pulling force is one of the signals that tells your skeleton to stay strong. Low lean mass, sometimes called sarcopenia, often travels together with low bone density, a combination called osteosarcopenia.
Body composition is tracked as one piece of a bigger picture alongside bone density scans, grip strength, and balance. It tends to change faster than bone density does, so it can show meaningful shifts in muscle and fat over months, while a bone density scan may take a year or longer to show a difference.
How sure is this?
Graded Emerging Evidence: Promising research, but findings are still developing and may be primarily from laboratory or animal studies. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
Tracking muscle, fat, and bone together gives a fuller picture of your fracture risk than weight alone.
Where this leads
WordYou just learned muscle helps keep bones loaded and strong. Curious why lean mass specifically gets tracked for bone health? Here is why it matters.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Related words
Lean mass is mostly your muscle weight — the non-fat part of your body. It's tracked because it's closely linked to…
Sarcopenia is the gradual loss of muscle mass and strength that comes with aging, and it's closely tied to bone health.
Osteosarcopenia is when a person has both osteoporosis (weak, low-density bone) and sarcopenia (loss of muscle mass…
InBody is a body composition analyzer that uses a painless electrical current (bioelectrical impedance) to estimate…
A DEXA scan is a low-radiation X-ray test that measures how much mineral is in your hip and spine bones, giving you…
Grip strength is how hard you can squeeze with your hand, measured with a device called a dynamometer. It's used as…
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
