Sarcopenia: Are We Diagnosing the Correct Muscle Problem?

An article written by Dr Edward Leatham, Consultant Cardiologist     © 2025 E.Leatham

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Why this matters in a cardiometabolic clinic

As we age, losing muscle is often described as inevitable — something to be measured, accepted, and quietly managed. Doctors call this process sarcopenia, and for many years it was defined largely as an age-related loss of muscle mass.

But modern research is challenging that view.

It turns out that how strong your muscles are may matter more than how big they look — particularly when it comes to independence, metabolic health, and long-term outcomes. [1,2]

Muscle mass vs muscle strength — what’s the difference?

Although they sound similar, muscle mass and muscle strength are not the same.

• Muscle mass refers to how much muscle tissue you have, often estimated using DEXA scans, bioimpedance scales, or body measurements.
• Muscle strength refers to how well that muscle works — how much force it can produce and how effectively it performs everyday tasks.

With ageing, these two measures often diverge.

Many people maintain a reasonable amount of muscle mass on scans, yet become noticeably weaker. This selective loss of strength is known as dynapenia. [3]

Strength declines faster than muscle size with ageing

Research consistently shows that muscle strength declines more rapidly than muscle mass as we get older. [3,4]

This happens because strength depends on far more than muscle size alone, including:

• nerve supply to muscle fibres
• coordination of motor units
• muscle fibre quality
• mitochondrial function
• regular mechanical loading and use

As a result, muscle can appear “preserved” on imaging while function quietly deteriorates.

This explains a common experience:

“I don’t look much thinner — but I feel weaker, slower, and less steady.”

Why strength matters more for real-world health

When researchers study outcomes that matter to people — not just scan results — muscle strength consistently outperforms muscle mass as a predictor.

Lower strength is associated with:

• reduced mobility
• higher risk of falls
• loss of independence
• longer hospital stays
• increased all-cause mortality
• Simple tests such as hand-grip strength often predict future health outcomes better than detailed body composition measurements. [4,5]

For this reason, modern medical definitions of sarcopenia now prioritise muscle strength, using muscle mass as supporting rather than primary information.1

What about metabolism — doesn’t muscle mass still matter?

Yes — muscle mass does matter metabolically.

Skeletal muscle:

• plays a major role in glucose disposal
• acts as a reservoir for amino acids
• contributes to resting energy expenditure

However, an important nuance is often missed:

Not all muscle tissue is equally metabolically effective.

Two people with similar muscle mass may have very different:

• insulin sensitivity
• glucose handling
• fatigue levels
• physical capacity

This appears to reflect muscle quality, activation, and use, rather than size alone. [2,5]

In other words, muscle that is weak, poorly activated, or rarely challenged may not behave like healthy metabolic tissue — even if it looks adequate on a scan.

Strength as a window into muscle quality

Muscle strength acts as a summary marker of overall muscle health.

It reflects:

• neural input to muscle
• efficiency of contraction
• habitual physical demand
• underlying metabolic function

This likely explains why strength tracks so closely with clinical outcomes — it captures information that imaging alone cannot. [2,4,6] Strength is not about athletic performance; it is about how well your body functions day to day.

A note for people losing weight — with or without GLP-1 medications

Many people actively losing weight — whether through dietary change alone or with the support of GLP-1 medications — worry about sarcopenia or “losing muscle.”

Some reduction in measured muscle volume during weight loss is normal and does not automatically indicate harmful muscle loss. Muscle contains glycogen and water, both of which fall with calorie restriction, and small amounts of intramuscular and surrounding subcutaneous fat also reduce as body fat falls. Together, these changes can make muscles appear smaller on tape measures, DEXA scans, or bioimpedance devices — even when muscle function is preserved.

For this reason, tracking strength during weight loss is often more meaningful than focusing on muscle size alone. At SCVC we use the VAT Trap  strength assessment tool to gauge and track strength in our patients.

The strength assessment accessed by click on the icon above uses a simple sit to stand assessment in 30 seconds and grip meter to gather objective information on upper and lower body strength.

GLP-1 medications and muscle: separating fact from fear

Myth: “GLP-1 medications cause muscle wasting or permanently damage muscle.”
Fact: There is no good evidence that GLP-1 medications directly harm skeletal muscle tissue.⁶

What people often observe instead is:

• reduced muscle glycogen and water
• loss of fat within and around muscle
• overall reduction in body size

These changes may be reported as “lean mass loss” by scans, but this is not the same as losing functional muscle.

An important caution: appetite suppression and protein intake

There is, however, an important exception.

In some patients using higher or rapidly escalated doses of GLP-1 medication, appetite suppression can become so pronounced that daily protein intake falls too low. When this happens, the body may begin to break down skeletal muscle to release essential amino acids needed for cell repair and vital functions. In this situation, weight loss can include true muscle loss, with potential effects on both muscle mass and strength.

This is not a direct toxic effect of the medication on muscle, but a consequence of inadequate nutritional intake, particularly protein, during aggressive appetite suppression.

Preserving muscle during weight loss therefore requires active management, not just calorie reduction.

In our clinic, patients undergoing a metabolic reset — including those using micro-dosed GLP-1 therapy — use an AI-supported food tracking app to monitor daily protein intake. Alongside simple strength tests such as hand-grip strength and the sit-to-stand test, this allows us to identify early warning signs and intervene, ensuring that weight loss is driven primarily by fat reduction while muscle strength and function are preserved.

Are we measuring the wrong thing?

For decades, medical assessment focused on how much muscle people had.

The evidence now suggests we should ask a different first question:

How well does that muscle work?

Muscle mass still matters — but mass alone is not enough to understand ageing, metabolic health, or future risk. [2,7]

The take-home message

• Muscle mass and muscle strength are not the same
• Strength declines faster than mass with ageing
• Strength predicts health outcomes better than size alone
• Muscle mass remains important, but incomplete
• During weight loss, maintaining strength and adequate protein intake is essential

So when we talk about muscle loss with ageing or weight loss, the key question may not be:

“How much muscle have you lost?”

But:

“How well does your muscle still work?”

References

(1) Cruz-Jentoft, A. J.; Bahat, G.; Bauer, J.; Boirie, Y.; Bruyère, O.; Cederholm, T.; Cooper, C.; Landi, F.; Rolland, Y.; Sayer, A. A.; Schneider, S. M.; Sieber, C. C.; Topinkova, E.; Vandewoude, M.; Visser, M.; Zamboni, M.; Writing Group for the European Working Group on Sarcopenia in Older People 2 (EWGSOP2), and the E. G. for E. Sarcopenia: Revised European Consensus on Definition and Diagnosis. Age Ageing 2019, 48 (1), 16–31. https://doi.org/10.1093/ageing/afy169. 

(2) Wolfe, R. R. The Underappreciated Role of Muscle in Health and Disease. Am. J. Clin. Nutr. 2006, 84 (3), 475–482. https://doi.org/10.1093/ajcn/84.3.475. 

(3) Clark, B. C.; Manini, T. M. What Is Dynapenia? Nutr. Burbank Los Angel. Cty. Calif 2012, 28 (5), 495–503. https://doi.org/10.1016/j.nut.2011.12.002. 

(4) Newman, A. B.; Kupelian, V.; Visser, M.; Simonsick, E. M.; Goodpaster, B. H.; Kritchevsky, S. B.; Tylavsky, F. A.; Rubin, S. M.; Harris, T. B.; on Behalf of the Health, A. and B. C. S. I. Strength, But Not Muscle Mass, Is Associated With Mortality in the Health, Aging and Body Composition Study Cohort. J. Gerontol. Ser. A 2006, 61 (1), 72–77. https://doi.org/10.1093/gerona/61.1.72. 

(5) Goodpaster, B. H.; Park, S. W.; Harris, T. B.; Kritchevsky, S. B.; Nevitt, M.; Schwartz, A. V.; Simonsick, E. M.; Tylavsky, F. A.; Visser, M.; Newman, A. B.; for the Health ABC Study. The Loss of Skeletal Muscle Strength, Mass, and Quality in Older Adults: The Health, Aging and Body Composition Study. J. Gerontol. Ser. A 2006, 61 (10), 1059–1064. https://doi.org/10.1093/gerona/61.10.1059. 

(6) Celis-Morales, C. A.; Welsh, P.; Lyall, D. M.; Steell, L.; Petermann, F.; Anderson, J.; Iliodromiti, S.; Sillars, A.; Graham, N.; Mackay, D. F.; Pell, J. P.; Gill, J. M. R.; Sattar, N.; Gray, S. R. Associations of Grip Strength with Cardiovascular, Respiratory, and Cancer Outcomes and All Cause Mortality: Prospective Cohort Study of Half a Million UK Biobank Participants. 2018. https://doi.org/10.1136/bmj.k1651. 

(7) López-Bueno, R.; Andersen, L. L.; Koyanagi, A.; Núñez-Cortés, R.; Calatayud, J.; Casaña, J.; del Pozo Cruz, B. Thresholds of Handgrip Strength for All-Cause, Cancer, and Cardiovascular Mortality: A Systematic Review with Dose-Response Meta-Analysis. Ageing Res. Rev. 2022, 82, 101778. https://doi.org/10.1016/j.arr.2022.101778. 

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