Lean mass
Also called: lean body mass
What it means
Lean mass is mostly your muscle weight — the non-fat part of your body. It's tracked because it's closely linked to strength, bone health, and fall risk.
Keeping lean mass up supports muscle strength and balance, which matters for reducing falls — a leading cause of fractures.
Lean mass is the part of your body weight that isn't fat — mostly muscle. It's tracked alongside bone density because muscle and bone are closely linked: stronger muscles generally mean more force going through your skeleton, and losing lean mass tends to go hand in hand with losing bone and strength overall.
Lean mass is measured using body composition tools like InBody scans, alongside grip strength, lower-limb strength, and balance. These measures change faster than bone density does, so tracking lean mass can show meaningful shifts months before a bone scan would show anything, giving a more realistic sense of progress over time.
Certain situations cause lean mass to drop quickly alongside bone loss. Androgen deprivation therapy for prostate cancer and aromatase inhibitor therapy for breast cancer both suppress sex hormones and accelerate loss of bone and lean mass together. Bariatric surgery can do the same, through reduced nutrient absorption, rapid weight loss, and lower mechanical loading. Anyone in these situations benefits from having an explicit, monitored plan with their care team.
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.
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.
Questions people ask about this
Between sessions, focus on four things: weight-bearing activity most days, resistance training a couple times a week, daily balance practice, and at least one rest day. This daily movement doesn't replace what happens during your session, but it supports your muscles, circulation, and balance, which all work alongside your bones.
Read the full answer →Related words
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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.
