Muscle Loss After 40 (Sarcopenia): How Fast It Happens, Why It Matters, and How a DEXA Scan Measures It

Most people notice weight, not muscle. Yet the amount of muscle you carry, and how strong it is, is one of the better predictors of how well you will move in your seventies and eighties. The medical name for age-related muscle loss with weakness is sarcopenia. This article sets out what the definition is, what the numbers say about speed and risk, what helps, and where a DEXA scan fits.

What is sarcopenia, and how is it diagnosed?

The European consensus (EWGSOP2, 2019) defines it in three levels. Sarcopenia is "probable" when low muscle strength is detected. It is "confirmed" by the presence of low muscle quantity or quality. It is "severe" when low strength, low muscle quantity or quality, and low physical performance are all found.

The consensus cut-offs are below.

Appendicular means the arms and legs. ASM is the lean muscle mass in those four limbs. Other expert groups use different cut-offs, so a result from one report is not directly comparable with another.

How common is it?

A 2022 systematic review and meta-analysis by Petermann-Rocha and colleagues pooled 151 studies with 692,056 participants (mean age 68.5 years). The prevalence of sarcopenia ranged from 10% to 27%, and severe sarcopenia from 2% to 9%. The range is wide because the answer depends on the definition and cut-off points used.

Among people under 60, the review found a range of 8% to 36%. That is not a reason to expect a diagnosis at 45. It shows that the studies in younger groups were heterogeneous and that low muscle is not only a problem of the very old.

How fast do muscle and strength fall with age?

There is no single answer, and the age at which decline starts is itself disputed. A 2012 quantitative review in Frontiers in Physiology notes that onset has been reported at 27 years, at 45 years and at 60 years in different studies. The same review says that muscle mass is almost static from 18 to 60 in one large DXA study.

The better-measured numbers come from following the same people over time. At about age 75, the review reports that muscle mass is lost at 0.64 to 0.70% a year in women and 0.8 to 0.98% a year in men. At that age, strength is lost at 3 to 4% a year in men and 2.5 to 3% a year in women. Studies that measured both in the same sample found strength falling 2 to 5 times faster than mass.

The Health ABC cohort shows the same pattern over five years. In 1,678 ambulatory, well-functioning adults, men lost 16.1% of leg muscle torque and women lost 13.4%. The annual loss of torque was 2 to 5 times greater than the loss of muscle area. Weight gain did not prevent the loss of strength.

Two points follow. First, these rates were measured in older adults, not in 40-year-olds, and we are not aware of a reliable figure for the 40s that we could cite. Second, strength is lost faster than size, so a scan of mass alone can look reassuring while the muscle weakens.

Why does it matter?

A 2022 meta-analysis in Gerontology (Xu et al.) pooled 56 studies with 42,108 participants. Sarcopenia was associated with a significantly higher risk of mortality, with a pooled hazard ratio of 2.00 (95% CI 1.71 to 2.34). The authors report that this association was independent of population, sarcopenia definition and follow-up period.

A 2019 systematic review by Yeung and colleagues covered 36 studies and 52,838 people; 33 of them (45,926 people) were pooled in the meta-analysis of falls and fractures. Sarcopenic people had higher odds of falling (odds ratio 1.60 in cross-sectional studies, 1.89 in prospective studies). For fractures the odds ratios were 1.84 and 1.71. These are associations in observational studies, so they do not prove that low muscle alone is the cause.

What helps?

The best-supported tool is resistance training. A 2021 meta-analysis of 14 randomized trials (561 older adults with sarcopenia, aged 65.8 to 82.8) found that resistance training was associated with improvements in body fat mass, handgrip strength, knee extension strength, gait speed and timed up-and-go performance. The effect on muscle mass was not statistically significant (standardized mean difference 0.27, 95% CI -0.02 to 0.56). In plain terms, training mainly made people stronger and faster, not clearly bigger.

For the general adult population, the US CDC recommends at least 2 days a week of muscle-strengthening activity that works all major muscle groups (legs, hips, back, abdomen, chest, shoulders and arms). A supervised program is worth asking about if you are already weak or have had a fall.

How does a DEXA scan measure muscle?

DEXA (dual-energy X-ray absorptiometry) splits the body into fat, lean soft tissue and bone, and reports each by region. That regional split is what produces the arm and leg lean mass used in the ASM and ASM/height² cut-offs above. The EWGSOP2 paper states that DXA is presently favored by some clinicians and researchers for measuring muscle mass, and recommends evaluating muscle by DXA and BIA methods in usual clinical care.

A DEXA result is a number to read with your history, not a diagnosis by itself. Our guide to how DEXA scans differ explains what the report contains. The same scan also reports bone density, covered in our bone density article.

Where does a muscle check fit in a screening visit?

The DEXA Total Body & Bone Health Package is $109 (book here). It reports body composition (fat, lean mass and a visceral fat estimate) and bone density, and it is sold as an add-on or a la carte. If you also want whole-body imaging, the Complete package at $1,699 (details) is a full-body MRI that includes DEXA body composition and bone density. Our health screening page lists the full range.

The limits are real. DEXA does not measure grip strength or walking speed, so it cannot on its own tell you whether you have sarcopenia. Grip and gait are simple tests that your own doctor can do. If your results or your own sense of getting weaker worry you, talk to a doctor about what to do next.

This article is for general education and is not medical advice.

Sources

• Age and Ageing — Cruz-Jentoft AJ et al., Sarcopenia: revised European consensus on definition and diagnosis (EWGSOP2) (accessed 2026-10-29)
• J Cachexia Sarcopenia Muscle — Petermann-Rocha F et al., Global prevalence of sarcopenia and severe sarcopenia: a systematic review and meta-analysis (2022) (accessed 2026-10-29)
• Frontiers in Physiology — Mitchell WK et al., Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review (2012) (accessed 2026-10-29)
• Am J Clin Nutr — Delmonico MJ et al., Longitudinal study of muscle strength, quality, and adipose tissue infiltration (2009) (accessed 2026-10-29)
• Gerontology — Xu J et al., Sarcopenia is associated with mortality in adults: a systematic review and meta-analysis (2022) (accessed 2026-10-29)
• J Cachexia Sarcopenia Muscle — Yeung SSY et al., Sarcopenia and its association with falls and fractures in older adults: a systematic review and meta-analysis (2019) (accessed 2026-10-29)
• Eur Rev Aging Phys Act — Chen N et al., Effects of resistance training in healthy older people with sarcopenia: a systematic review and meta-analysis of randomized controlled trials (2021) (accessed 2026-10-29)
• US Centers for Disease Control and Prevention — Adult Activity: An Overview (accessed 2026-10-29)

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