Osteoporosis is a condition characterized by reduced bone density and deteriorated bone tissue structure, increasing fracture risk, particularly at the hip, spine, and wrist, more common in older adults and postmenopausal women specifically. This entry is worth reading with a different expectation than several others in this encyclopedia. There is deliberately no bone density risk score, an honest gap rather than an invented, weakly-supported score.
- Reduced bone density and structure, increasing fracture risk, particularly hip, spine, and wrist.
- Bone density is deliberately excluded from the risk categories, no strong direct marker link exists yet.
- A DEXA scan is the clinical gold standard for directly measuring bone mineral density.
- Typically recommended starting around age 65 for women, earlier with specific risk factors.
Why a scoring model should leave this out
A risk framework that groups markers by the disease they predict should exclude any category where the markers don’t have a strong enough direct evidence link, osteoporosis and cancer risk are specifically named as excluded for exactly this reason, rather than being forced into the framework with a weak, invented association. None of the markers currently tracked, body composition, cardiovascular fitness, strength, functional capacity, have strong enough direct evidence specifically linking them to bone mineral density to justify treating them as a reliable bone density risk proxy.
This is a deliberate choice to stay honest about the limits of what these particular tracked markers can actually tell you, rather than manufacturing false reassurance or false alarm by stretching markers designed for other purposes into a role they don't have solid evidence to support.
What actually assesses bone density risk
A DEXA scan, dual-energy X-ray absorptiometry, is the clinical gold standard for directly measuring bone mineral density, a dedicated test that no tracked marker substitutes for. Standard clinical guidance recommends this screening starting around age 65 for women, and earlier for people with specific risk factors, including early menopause, certain medications, or a family history of osteoporosis, worth discussing directly with a doctor rather than relying on general fitness or body composition markers as a stand-in.
How bone density is actually assessed, and what moves it
Bone density can’t be inferred from any of the markers tracked here, which is why it isn’t scored. That doesn’t make it unimportant, and the assessment is straightforward enough to be worth understanding.
The T-score
A DEXA scan measures bone mineral density and reports it as a T-score: standard deviations from the mean of a healthy young adult.
- Above -1.0. Normal.
- -1.0 to -2.5. Osteopenia, meaning reduced density without meeting the osteoporosis threshold.
- -2.5 or below. Osteoporosis.
- -2.5 or below plus a fragility fracture. Severe or established osteoporosis.
A Z-score, comparing against age-matched peers rather than young adults, is used for premenopausal women, younger men and children, where the young-adult comparison would be misleading.
Why the threshold is less decisive than it looks
Most fragility fractures occur in people with osteopenia rather than osteoporosis, simply because far more people fall into that band. Density is one input to fracture risk alongside fall probability, bone geometry and tissue quality, none of which a T-score captures. Tools such as FRAX combine density with clinical risk factors for this reason.
What actually builds and preserves bone
- Mechanical loading above habitual levels. Bone adapts to strains it doesn’t already experience. Walking is a load your skeleton is thoroughly adapted to, which is why walking programs produce disappointing density results. Progressive resistance training and impact activity provide the stimulus.
- Adequate protein and calcium. Bone matrix is roughly half protein by volume, and low protein intake is associated with worse bone outcomes.
- Vitamin D sufficiency. Required for calcium absorption, covered in vitamin D3.
- Avoiding prolonged immobility. Bed rest and immobilisation cause losses far faster than aging does.
Peak bone mass is reached in the twenties, and everything after is a question of how slowly it is lost. That makes this one of the few areas where the most valuable action happens decades before the measurement would show anything.
How bone density is measured and scored
Bone density has a well-established measurement standard and a clinical diagnostic test, which is precisely why estimating it from markers that cannot support the inference produces a number that looks authoritative and is not.
DEXA and the T-score
The reference test is a DEXA scan of the hip and lumbar spine. Results are expressed as a T-score: standard deviations from the mean of a healthy young adult.
- Normal: T-score of -1.0 or above.
- Osteopenia: between -1.0 and -2.5. Reduced density, not yet osteoporosis, and the stage where intervention has most to work with.
- Osteoporosis: -2.5 or below.
- Severe osteoporosis: -2.5 or below plus one or more fragility fractures.
A Z-score, comparing against others of the same age and sex, is used instead for younger adults and children, where comparison against a young-adult peak isn’t meaningful.
Why density alone under-predicts fractures
Most fragility fractures occur in people with osteopenia rather than osteoporosis, simply because far more people fall in that band. That changes what a T-score between −1.0 and −2.5 should prompt.
It also means balance and lower-body strength are part of fracture prevention rather than a separate topic. This app cannot estimate your bone density, and the markers it does track bear directly on whether you fall: single-leg balance and the sit-to-stand test measure exactly that capacity.
Most fragility fractures occur in people with osteopenia rather than osteoporosis, simply because far more people fall in that band. Density is one input into bone strength; architecture, turnover rate and, critically, whether you fall at all matter too.
This is why fracture risk calculators such as FRAX combine density with age, prior fracture, parental hip fracture, smoking, steroid use and other factors to estimate ten-year probability. It also means balance and lower-body strength are part of fracture prevention rather than a separate topic.
What actually builds bone
Bone responds to loads meaningfully above what it already experiences, which is why walking maintains rather than builds. The stimuli with evidence behind them are progressive resistance training, particularly compound movements loading the spine and hip, and impact activity such as jumping or hopping where joints permit it.
Nutrition is permissive rather than driving: adequate calcium and vitamin D allow mineralisation to occur but don’t stimulate it. This is the likeliest explanation for why calcium supplementation alone has performed poorly in fracture trials while loading plus adequate intake performs well.
Tracked markers vs. dedicated bone density testing
| This App's Tracked Markers | DEXA Bone Density Scan | |
|---|---|---|
| Measures | Body comp, cardio, strength, function | Actual bone mineral density directly |
| Evidence link to osteoporosis risk | Not strong enough to include | The direct, clinical gold standard |
| Recommended use | General health tracking | Dedicated screening, per doctor guidance |
Diagnostic thresholds from the WHO 1994 report.
Where a fitness app stops being useful for bone density
Consumer health tools often claim comprehensive risk coverage across every condition, stretching whatever markers they happen to track into categories the evidence doesn’t support.
Bone density is one of those categories. None of the markers tracked here has strong enough direct evidence linking it to bone density, and saying so is more useful than producing a number that looks like an answer.
If you are in a higher-risk group, postmenopausal, over 65, or carrying specific risk factors, discuss dedicated DEXA screening with a doctor rather than relying on general fitness tracking. Resistance training does have separate, well-supported benefits for bone.
The app is honest about this gap, no invented bone-density score.
Sources
Key references for the claims on this page. Where a figure is attributed to a specific study or body, it is named here.
- World Health Organization. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. 1994. Origin of the T-score thresholds used here.
- Kanis JA, et al. FRAX fracture risk assessment tool documentation.
- Bolland MJ, Leung W, Tai V, et al. Calcium intake and risk of fracture: systematic review. BMJ. 2015;351:h4580. Underpins the caution on calcium supplementation alone. DOI
Frequently asked
What is osteoporosis?
Reduced bone density and structure, increasing fracture risk, particularly hip, spine, and wrist.
Why isn’t there a bone density score?
None of the tracked markers have strong enough direct evidence linking them to bone density, an honest gap.
How is bone density risk actually assessed?
A DEXA scan is the clinical gold standard, typically starting around age 65 for women.
How do you know if you have osteoporosis?
A DEXA scan measuring bone mineral density is the standard diagnostic test. There are usually no symptoms beforehand, which is why the first indication for many people is a fracture from a minor fall.
What is a T-score?
The comparison of your bone density against a healthy young adult reference. Between minus one and minus two point five is classified as osteopenia, and below minus two point five as osteoporosis.
Does walking build bone density?
Not much. Bone responds to loads meaningfully above what it already experiences, and walking is a load it is thoroughly adapted to. Resistance training and impact activity provide the stimulus that walking doesn’t.
Do calcium supplements prevent fractures?
The evidence for calcium supplementation alone reducing fractures is weaker than the widespread recommendation implies. Adequate dietary calcium, sufficient vitamin D and mechanical loading together make a stronger case than pills alone.
Who should have a bone density scan?
Postmenopausal women, older men, and anyone with risk factors such as long-term steroid use, previous low-trauma fracture or a strong family history. It is a conversation to have with a doctor rather than something to self-refer for.